iOS 14 requestTrackingAuthorization status always denied

The thing that finally worked for me was a "General->Reset->Reset All Content and Settings".

Then when I installed my app the prompt appeared and I could select to Allow tracking. Afterwards my app appeared in Settings, which it had not before, and on tapping it there's an option to disable/enable tracking. The app also now appears in Privacy/Tracking, which it did not before.

I tested further by deleting the app and reinstalling, and again it showed the message to allow tracking.

The only reason I can think ATT does not work as expected is that all apps installed prior to iOS 14.4 / ATT are assumed to be set to "do not allow tracking," but the OS misses adding the app to the Settings page so there's no way of changing it. Although, this does not explain why an uninstall/reinstall of the app still doesn't work.

In conclusion, creating a fresh app might work (untested), but factory reset definitely does work.

Apple released iOS and iPadOS 14.5.1. According to Apple's release notes, the update fixes a bug with App Tracking Transparency that may have prevented some users from receiving prompts from apps.

Release notes for iOS and iPadOS 14.5.1

This update fixes an issue with App Tracking Transparency where someusers who previously disabled Allow Apps to Request to Track inSettings may not receive prompts from apps after re-enabling it. Thisupdate also provides important security updates and is recommended forall users.

Updated OS, now I can see ATT dialog.