A Microsoft file hosting and synchronization service.
So thankful to find others with the same problem that I have had for months. Misery loves company.
I actually thought it was something I had done and have struggled to find a fix. I don't know why previous searches with similar question wording did not lead me to these threads.
I was able to get an email back from a Microsoft supervisor... while I " was dear to them" (honestly parts of the English sounded like a phishing email)
Please be advised that our support engineers do not have control over these limitations. We continue to send insights to our engineering team to further improve how our systems work and rest assured that we will do that on your case as well.
So angry for all the wasted time over what is supposed to be a convenience.. and one they charge for!