Processes in Microsoft 365 for setting up Office apps, redeeming product keys, and activating licenses.
Hi, Adam Sonne Stæhr
Welcome to the Microsoft Community.
Understand that your issue is that when logging into the Planner app on your Android phone, you are experiencing that the app is stuck on the loading screen, but it works fine when logging in using another account within the same organization.
I wish I could answer your question directly, but since Planner-related questions require more specialized technical information to help you solve them, there is a special section in Microsoft learn (English only) for this issue. The experts there may know more about how to solve your problem.
Here is a link to the forum: Partner Center.
You can ask for specifics and share ideas for solving your problem in the forum.
Finally, while I can't help you further, I hope the information I've provided will help you find a better direction. Hopefully, your issue can be resolved after contacting the appropriate channel.
Sincerely,
Cherry.Z - MSFT | Microsoft Community Support Specialist