Can't rebuild mailbox in Apple Mail

Hello, I am running Apple Mail 15.0 in OS Monterey 12.2. Since I upgraded to Monterey my work account from Microsoft Exchange won' t work properly. Currently all the messages show up blank in Apple Mail. I was told to rebuild the main mailbox for that account. When I have rebuilt mailboxes before, they go blank for a while and then the messages come back. But in this case nothing happens, the mailbox does not go blank, thus it appears it is not rebuilding.

Help!