I have created an app and has been live since Sept 2020 (based on Sharepoint List) In the past week I have added 4 users to access the same. 3 of them had no problems accessing and interacting with it. One user accesses the app, however, no data is shown and the user is unable to add or remove records. I have noticed that there is an error bar on top, but it disappears very quick.
Note: All users were added to Powerapps and SharePointList Note: user is able to interact with other Apps
I would go back and make sure the users have desired rights to teams permission, PowerApps program permission and SharePoint areas. then would try adding a new users and seeing if the issue happens, if not then remove there rights and add the rights back in each.
Lets not forget there is bunch of stull that has to be in line and sometimes it does not work perfectly.