Hi Cripken2,
Thanks for your reply. Now I understand that some users encounter the sign-in error on iPhone.
I’d like to clarify that Microsoft Teams is available on the following mobile platforms:
IOS 9.0+, Android 4.4+, Windows Phone 10.0.10586+.
From the screenshot, I noticed that you are trying to connect the Microsoft Teams app through WiFi. It is suggested that you change the network environment to check if there is any improvement.
Also, we will appreciate it if you can provide following information so that we can try reproducing the issue on our side.
1. The iOS version. Please make sure it is 9.0+.
2. The Microsoft Teams app version.
3. One problematic account which meets the Sign-in-error. Please share it with us via the link below, and we will check the account status for you and do more analysis.
https://answers.microsoft.com/en-us/privatemessages/list
Thanks,
Lance