https Sub-Domain not redirecting correctly with htaccess

Question

I have a domain called: example.com and a subdomain called: sub.example.com

I want to force all primary domain requests for example.com to https:// except for 1 folder. Example:

http://www.example.com/ <-- Redirect all requests to https://
http://www.example.com/folder/ <-- Force to http:// not https://

I also want to force all subdomain requests for sub.example.com to https:// except for 1 folder. Example:

http://sub.example.com <-- Redirect all requests to https://
http://www.example.com/folder/ <-- Force to http:// not https://

Currently example.com is working fine and forces to https:// for the primary domain and the folder is not redirecting to https:// however the folder is not enforcing http:// if someone chooses https://

If i visit http://sub.example.com it does not enforce https:// and if I visit https://sub.example.com manually it shows as such in the url. However the website it displays is actually from https://www.example.com

The htaccess file i have for example.com is:

<IfModule mod_rewrite.c>

    RewriteEngine On
    RewriteCond %{SERVER_PORT} 80 
    RewriteCond %{HTTP_HOST} !^www.example.com$ [NC]        
    RewriteCond %{HTTP_HOST} !^sub.example.com$ [NC]
    RewriteCond %{REQUEST_URI} !^/folder/
    RewriteRule ^(.*)$ https://www.example.com/$1 [R=301,QSA,L]

 </IfModule>

The htaccess file i have for sub.example.com is:

RewriteEngine on
RewriteBase /
RewriteCond %{SERVER_PORT} 80 
RewriteCond %{REQUEST_URI} !^/folder/
RewriteCond %{HTTP_HOST} ^example\.com\.au$ [NC]
RewriteRule ^ https://www.%{HTTP_HOST}%{REQUEST_URI} [R=301,L] 

Answer 1

I found the issue. It was unrelated to the htaccess file. I found the certificate i had was installed onto the primary domain and the subdomain did not have a certificate that matched.

Apache was redirecting to the ssl certificates domain instead of the subdomain. I solved this by purchasing a wild card ssl, installing it onto the primary domain and then separately installing it onto the sub domain also.

This fixed the problem.