Hi, Thomas
Good day!
Thank you for posting to Microsoft Community. We are happy to help you.
According to your description, the issue of your concern that your Teams for Android device not allow you to join into a meeting.
Since everything is working well only except for the Teams for Android, thanks for your attempts from the above which is the basic trouble shooting way of that.
At this moment, we're afraid that we cannot give you a proper suggestion here.
Therefore, we would like to refer you to contact Microsoft Teams experts team - office-teams-windows-itpro who would conduct in-depth research on the problem you encountered and provide you with more professional assistance with more access and recourse.
We believe they will give you a quick respond and solve it soon for you.
Thanks for your time and your understanding would be highly appreciated.
Sincerely,
Alex | Microsoft Community Moderator.