Ad-hoc distributed app not downloading on iOS 14.0 and above

Question

I have an iPad app that is distributed ad-hoc to users within my organisation. To download the app, users:

1. Visit an internal web page in Safari
2. Click a link to a manifest file, which links to the.ipa file
3. Click 'Install' when prompted, which downloads the app to the iPad

We have tested on iOS 12.x and 13.x and the app downloads successfully. Since iOS 14.x however, the app fails to download, with the error:

Unable To Install (app name). Please try again later.

Can anyone advise? There have been similar reports online but no resolution yet:

• https://developer.apple.com/forums/thread/655207
• https://developer.apple.com/forums/thread/660618
• https://developer.apple.com/forums/thread/662428
• https://developer.apple.com/forums/thread/661432

Answer 1

When anything I do, ever, works on more than one generation of Apple products, I'm quite surprised and elated. It's like power adapters of the soul.