I've got a user who's AD account has been renamed (stephen.hawkes to steve.hawkes). This has been synced to Azure AD and reflects correctly in admin.microsoft.com and on the Azure portal.
However, in Microsoft Teams he continues to be shown as Stephen not Steve. Two days after the rename. I've forcibly signed him out of all sessions to ensure he's logging in fresh, but he still shows as Stephen.
Anecdotally I've read in various forums (including here) that it can take Teams several days to pick up account changes such as the display name, profile picture, etc. Why is this? What can I do about it? More importantly what are Microsoft doing about it? It's really poor.
There are multiple syncs that need to happen on the backend, and there's nothing you can do until they complete. Then, there is the client cache factor, which might add additional delays. If you can see the new name in the Teams admin center, you can assume the backend sync is done, so you can try clearing Teams cache or open a private session in the browser.