It sounds like you’re having the same problem that I’m having on my Windows 10 machine running outlook 2019. After trying a few different approaches, what I ended up doing was deleting the account from Outlook and adding it back in. Except I feel like it still isn’t really right. But I think that might be a different thread something like IMAP versus pop three. I expect this might be what you end up doing as well. Good luck with it because it took me a whole day to figure it out and get things working again.