One of my user accounts is not syncing changes from on prem AD to Entra AD via Entra AD Sync.

One of my user accounts is not syncing changes from on prem AD to Entra AD via Entra AD Sync. The username was originally misspelled and was synced via Entra AD Sync to Azure with the incorrect spelling. I was able to adjust the username in our On prem AD and initiated a delta using Entra AD Sync. The new username shows in Entra AD but the UserPrincipalName is not updating in Entra AD.

I then deleted the user account in Entra AD and let Entra AD Sync push the user again. The same thing happened where the user was added back correctly except for the UserPrincipalName. I thought about deleting the user again and permanently deleting the user, but the documentation says that the user cant be added back in (not even by support). Im not sure if this means it cant be added back via Entra AD Sync, so I did not continue.

I am not receiving any errors from Entra AD Sync in reference to the sync for this specific user. The Sync for this user has a successful status (when I originally noticed the issue and after I deleted and re-added the user in our on prem AD).

How can I get my user's correct UPN into Azure AD?