Hi there!
I had an issue with 2FA on my O365 install and their support asked me to disable my Azure AD Connect. When I attempted to do this, it looks as though it broke my sync. I went to try and enable it again today, I have had issues with getting it synced back up. I cannot sign back in, it just stalls when trying to login. I then tried to disable the directory sync on the Azure side, but it seems to be stuck in Active/Disabling and it doesn't seem to want to correct itself.