Configuring preferences and options in Outlook.com
There may not be a single fix that works for everyone, but what I posted earlier worked for me, and has continued to work for the past 10 days.
I'm using a Moto G6 play with android 9, and the usual Gmail app that comes with it to connect to a hotmail account for email, contacts & calendar data.
My fix was basically this: uninstalled the Gmail app (updates), deleted my hotmail account from the phone and then reconnected it as explained in my earlier post. After giving the OK for permissions required everything worked again; email, contacts & calendar.
But I did not realize I still had auto-updates turned on for all apps, the Gmail app soon updated itself again back to the newest version which I thought caused the problem. But it still continued to work anyway!!!
So the common denominator I see reading through all these posts seems to be app permissions, which get reset when trying various app version updates or fixes.
FYI - the November 5 Gmail app update that seemed to break things for me was (from my notes)
version: 2019.10.20.278647676.release
after "Uninstall updates" (under the 3-dot menu in App info), it reverted to
version: 9.2.3.235065705.release
and within an hour, it auto-updated back to the newer version (above) which continues to work just fine.
I did finally find out how to turn off app auto-updates: it's a menu setting in the Google Play store app.