Does anyone else have the same issue?
Could you log in with other mobiles?
I didn’t get an iPhone 12 Pro Max. I only tested in iPhone 12 (version: 14.3). It worked with no problem.
To exclude account side issue, try to log in other types of Teams client, such as desktop client, web client. Then, observe the results.
Besides, you could contact your IT administrator to check if he creates some conditional access policies in Azure Active Directory admin center to block the mobile platform in Teams.
For more details about Conditional Access, refer to by this link.
If the response is helpful, please click "Accept Answer" and upvote it.
Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.