Here is what worked for me, after weeks of frustration. I realized that Google was trying to protect my account from becoming corrupted due to sync error, especially after PC Windows updates. :
Remove your GMail account from Outlook on all PCs, and your phone (all devices) by doing this:
Sign in to your Google Account, navigate to the Security section, and then under "Your devices," click "Manage all devices." You'll then be able to see all devices that are currently logged into your account. Sign out of ALL DEVICES even though some may be working fine.
Now sign back in on your PC with Outlook.
Then on any other devices.
The problem is mostly with Google, not Microsoft. But both companies should meet to figure out how to either solve the problem, or have a simple way to resolve it without doing the procedure above. Once I did the above, the problem has not returned.