Outlook web add-in manifest change to support mobile devices (mobileFormFactor) installation fails

Question

I'm trying to enable outlook web add-in for mobile by making below changes in manifest file but the installation fails and throws below error.

Error Message:

Manifest file:

<?xml version="1.0" encoding="UTF-8"?>
    <!--Created:ce44715c-8c4e-446b-879c-ea9ebe0f09c8-->
    <OfficeApp 
      xmlns="http://schemas.microsoft.com/office/appforoffice/1.1" 
      xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 

  xmlns:bt="http://schemas.microsoft.com/office/officeappbasictypes/1.0" 
      xmlns:mailappor="http://schemas.microsoft.com/office/mailappversionoverrides/1.0" 
      xsi:type="MailApp">

 <!-- Begin Basic Settings: Add-in metadata, used for all versions of 
Office unless override provided. -->

 <!-- IMPORTANT! Id must be unique for your add-in, if you reuse this 
  manifest ensure that you change this id to a new GUID. -->
  <Id>3a734653-a3ab-4021-ad93-8df9fce4e1e9</Id>

 <!--Version. Updates from the store only get triggered if there is a 
  version change. -->
 <Version>1.0.0.0</Version>
 <ProviderName>ABCTech</ProviderName>
 <DefaultLocale>en-US</DefaultLocale>
  <!-- The display name of your add-in. Used on the store and various 
  places of the Office UI such as the add-ins dialog. -->
 <DisplayName DefaultValue="testMobile" />
 <Description DefaultValue="testMobile"/>
 <IconUrl DefaultValue="~remoteAppUrl/Images/icon64.png"/>

 <SupportUrl DefaultValue="http://www.abctech.com" />
 <!-- Domains that will be allowed when navigating. For example, if you 
   use ShowTaskpane and then have an href link, navigation will only be 
 allowed if the domain is on this list. -->


    <AppDomains>
    <AppDomain>AppDomain1</AppDomain>
    <AppDomain>AppDomain2</AppDomain>
    <AppDomain>AppDomain3</AppDomain>
  </AppDomains>
  <!--End Basic Settings. -->
   <Hosts>
     <Host Name="Mailbox" />
    </Hosts>
  <Requirements>
    <Sets>
      <Set Name="Mailbox" MinVersion="1.1" />
    </Sets>
  </Requirements>
  <FormSettings>
    <Form xsi:type="ItemRead">
      <DesktopSettings>
        <SourceLocation DefaultValue="~remoteAppUrl/MessageRead.html"/>
        <RequestedHeight>250</RequestedHeight>
      </DesktopSettings>
    </Form>
  </FormSettings>

  <Permissions>ReadWriteItem</Permissions>
  <Rule xsi:type="RuleCollection" Mode="Or">
    <Rule xsi:type="ItemIs" ItemType="Message" FormType="Read" />
  </Rule>
  <DisableEntityHighlighting>false</DisableEntityHighlighting>

  <VersionOverrides xmlns="http://schemas.microsoft.com/office/mailappversionoverrides" xsi:type="VersionOverridesV1_0">
    <Requirements>
      <bt:Sets DefaultMinVersion="1.3">
        <bt:Set Name="Mailbox" />
      </bt:Sets>
    </Requirements>
    <Hosts>
      <Host xsi:type="MailHost">

        <DesktopFormFactor>
          <!-- Location of the Functions that UI-less buttons can trigger (ExecuteFunction Actions). -->
          <FunctionFile resid="functionFile" />

          <!-- Message Read -->
          <ExtensionPoint xsi:type="MessageReadCommandSurface">
            <!-- Use the default tab of the ExtensionPoint or create your own with <CustomTab id="myTab"> -->
            <OfficeTab id="TabDefault">
              <!-- Up to 6 Groups added per Tab -->
              <Group id="msgReadGroup">
                <Label resid="groupLabel" />
                <!-- Launch the add-in : task pane button -->
                <Control xsi:type="Button" id="msgReadOpenPaneButton">
                  <Label resid="paneReadButtonLabel" />
                  <Supertip>
                    <Title resid="paneReadSuperTipTitle" />
                    <Description resid="paneReadSuperTipDescription" />
                  </Supertip>
                  <Icon>
                    <bt:Image size="16" resid="icon16" />
                    <bt:Image size="32" resid="icon32" />
                    <bt:Image size="80" resid="icon80" />
                  </Icon>
                  <Action xsi:type="ShowTaskpane">
                    <SourceLocation resid="messageReadTaskPaneUrl" />
                  </Action>
                </Control>
                <!-- Go to http://aka.ms/ButtonCommands to learn how to add more Controls: ExecuteFunction and Menu -->
              </Group>
            </OfficeTab>
          </ExtensionPoint>
          <!-- Go to http://aka.ms/ExtensionPointsCommands to learn how to add more Extension Points: MessageRead, AppointmentOrganizer, AppointmentAttendee -->
        </DesktopFormFactor>
      </Host>
    </Hosts>

    <Resources>
      <bt:Images>
        <bt:Image id="icon16" DefaultValue="~remoteAppUrl/Images/icon16.png"/>
        <bt:Image id="icon32" DefaultValue="~remoteAppUrl/Images/icon32.png"/>
        <bt:Image id="icon80" DefaultValue="~remoteAppUrl/Images/icon80.png"/>
      </bt:Images>
      <bt:Urls>
        <bt:Url id="functionFile" DefaultValue="~remoteAppUrl/Functions/FunctionFile.html"/>
        <bt:Url id="messageReadTaskPaneUrl" DefaultValue="~remoteAppUrl/MessageRead.html"/>
      </bt:Urls>
      <bt:ShortStrings>
        <bt:String id="groupLabel" DefaultValue="My Add-in Group"/>
        <bt:String id="customTabLabel"  DefaultValue="My Add-in Tab"/>
        <bt:String id="paneReadButtonLabel" DefaultValue="Display all properties"/>
        <bt:String id="paneReadSuperTipTitle" DefaultValue="Get all properties"/>
      </bt:ShortStrings>
      <bt:LongStrings>
        <bt:String id="paneReadSuperTipDescription" DefaultValue="Opens a pane displaying all available properties. This is an example of a button that opens a task pane."/>
      </bt:LongStrings>
    </Resources>

    <VersionOverrides xmlns="http://schemas.microsoft.com/office/mailappversionoverrides/1.1" xsi:type="VersionOverridesV1_1">
      <Hosts>
        <Host xsi:type="MailHost">
          <MobileFormFactor>
            <FunctionFile resid="functionFile" />
            <ExtensionPoint xsi:type="MobileMessageReadCommandSurface">
              <Group id="mobileMsgRead">
                <Label resid="groupLabel"/>
              <Control id="mblRestButton" xsi:type="MobileButton">
                <Label resid="mblButtonLabel"/>
                <Icon xsi:type="bt:MobileIconList">
                  <bt:Image size="25" scale="1" resid="green-icon-32" />
                  <bt:Image size="25" scale="2" resid="green-icon-32" />
                  <bt:Image size="25" scale="3" resid="green-icon-32" />

                  <bt:Image size="32" scale="1" resid="green-icon-32" />
                  <bt:Image size="32" scale="2" resid="green-icon-32" />
                  <bt:Image size="32" scale="3" resid="green-icon-32" />

                  <bt:Image size="48" scale="1" resid="green-icon-32" />
                  <bt:Image size="48" scale="2" resid="green-icon-32" />
                  <bt:Image size="48" scale="3" resid="green-icon-32" />
                </Icon>
                <Action xsi:type="ShowTaskpane">
                  <SourceLocation resid="restMobileTaskPaneUrl"/>
                </Action>
              </Control>
              </Group>
            </ExtensionPoint>
          </MobileFormFactor>
        </Host>
      </Hosts>

      <Resources>
        <bt:Images>
          <!-- Green icon -->
          <bt:Image id="green-icon-16" DefaultValue="~remoteAppUrl/Images/icon16.png"/>
          <bt:Image id="green-icon-32" DefaultValue="~remoteAppUrl/Images/icon32.png"/>
          <bt:Image id="green-icon-80" DefaultValue="~remoteAppUrl/Images/icon80.png"/>
        </bt:Images>
        <bt:Urls>
          <bt:Url id="functionFile" DefaultValue="~remoteAppUrl/FunctionFile/Functions.html"/>
          <bt:Url id="restMobileTaskPaneUrl" DefaultValue="~remoteAppUrl/home.html"/>
        </bt:Urls>
        <bt:ShortStrings>
          <bt:String id="groupLabel" DefaultValue="Add-in Demo"/>
          <!-- Read mode -->
          <bt:String id="mblButtonLabel" DefaultValue="Test REST Calls"/>
        </bt:ShortStrings>
      </Resources>
    </VersionOverrides>
  </VersionOverrides>
</OfficeApp>

But the same manifest file works for the desktop version.The above manifest follows same structure as that of manifest in production which is a desktop version.

The requirement is to support the same plugin for mobile devices for both android and IOS.

This is the link which I followed to add mobileFormFactor element which is used to support Mobile Device.

------------------------------After Edit ------------------------------------

Here is the missing part which needs to be added before MobileFormFactor

<DesktopFormFactor>
        <FunctionFile resid="functionFile" />
        <ExtensionPoint xsi:type="MessageReadCommandSurface">
          <!--Use the default tab of the ExtensionPoint or create your own with <CustomTab id="myTab"> -->
          <OfficeTab id="TabDefault">
            <!--  Up to 6 Groups added per Tab  -->
            <Group id="msgReadGroup">
              <Label resid="groupLabel"/>
              <!--  Launch the add-in : task pane button  -->
              <Control xsi:type="Button" id="msgReadOpenPaneButton">
                <Label resid="paneReadButtonLabel"/>
                <Supertip>
                  <Title resid="paneReadSuperTipTitle"/>
                  <Description resid="paneReadSuperTipDescription"/>
                </Supertip>
                <Icon>
                  <bt:Image size="16" resid="icon16"/>
                  <bt:Image size="32" resid="icon32"/>
                  <bt:Image size="80" resid="icon80"/>
                </Icon>
                <Action xsi:type="ShowTaskpane">
                  <SourceLocation resid="messageReadTaskPaneUrl"/>
                </Action>
              </Control>
              <!--Go to http://aka.ms/ButtonCommands to learn how to add more Controls: ExecuteFunction and Menu -->
            </Group>
          </OfficeTab>
        </ExtensionPoint>
        <!--Go to http://aka.ms/ExtensionPointsCommands to learn how to add more Extension Points: MessageRead, AppointmentOrganizer, AppointmentAttendee-->
      </DesktopFormFactor>

Answer 1

将DesktopFormFactor及其对应的资源添加到VersionOverridesV1_1类型的VersionOverrides中有助于解决此问题。