Hi,
Please enable the Show Organization tab for users function in the Teams admin center
Also, if the problem has been unresolved, please go to the Exchange admin center > recipients > mailboxes > select user A and then remove the manager for user A, click Save, then wait for a while and re-add the manager for user A to see if this will make any difference.
Moreover, please click on the command box at the top of Microsoft Teams and type “/org”, then type the name of user A to check the result. For your reference:
In the meantime, please login to Teams web APP with the browser's InPrivate window to see if there is the same issue in there.
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