FWIW, I had a 'bang your head' moment that lasted a while that was a result of a change I was testing. While not Skynet related, I set a few of my clients, through DHCP reservations and an alternate DNS Server - to 'AdGuard' DNS servers. It was to try and filter out some of the commercials in various streaming services.
Two issues - 1) I had just wiped and reinstalled Windows 10 (2H20) when I could not get any email to sync. It seemingly accepted my GSuite Creds but nothing would ever come down. 2) Outlook Client on my iPhone stopped working as well. I removed the app and when I went to re-add it, I would get a 'page not found' error. (rendered like a web page, inside the IOS Outlook client).
Ironically an already set-up Win10 Mail client continued to work.
A week went by and by dumb luck stumbled back into the DHCP reservations and had that lightbulb moment.
Removing the DNS override fixed adding my GSuite account to IOS Outlook immediately. The Win10 client would not work, even after removing and re-adding the account, so I had to force remove and re-ins install the Mail/Calendar app. That worked.
Not the same as your issues but the commonality here is the live/outlook service sometimes doesn't play well with privacy and security manipulation.