A Microsoft file hosting and synchronization service.
Same issue as the rest. One day it worked, the next it did not. I am using about 1/3 of my 1 TB so space is not an issue.
I even disabled PV then re enabled it again and no fix. I created a new shared account with one of my 5 and same thing with new account with a full 1TB unused.
Come on MS, get your stuff together and respond to us.