Outlook doesn’t update at all.

I have two accounts on outlook, and the main one I have doesn't seem to update at all, while the other works just fine. I cannot receive any emails, I can't send any emails, and when I click on any unopened emails I already have, it doesn't even recognize that I opened it. Once I log back into outlook, that same email is highlighted as if I never opened it. I also cannot delete any emails either, or move any of them around.