Outlook stuck on "Loading Profile" stage

Outlook got stuck "not responding", as it does multiple times every day. A pop-up offered me the choice of restarting. I did and now it's stuck on the "Loading Profile" pop-up and goes no further. 

FYI, I've already been on this page - https://support.microsoft.com/en-us/office/outlook-not-responding-stuck-at-processing-stopped-working-or-freezes-5c313d04-64af-4441-82d2-44e5a43eee5a

and followed all 6 steps suggested. None of them fixed the issue. 

NB the issue only started when we migrated to 365, which has been a complete pain in the **bleep** since we did it.