My problem is similar but a little different. I am working on a new version of an existing app that utilizes either wifi or the cellular network to upload small amounts of data to icloud. Everything worked fine until I updated to iOS 14.01 and now my app refuses to access the cellular network. I have gone to settings->cellular and found the app under CELLULAR DATA and made sure that the switch for my app is turned on (and that cellular data is turned on) Still the app cannot access the cellular network. I can make calls and some apps continue to access my cellular data. I have tried to recompile my app using the newest version of xcode (12.0.1) but this doesn't help.
We need Apple to fix this.