MS Surface Pro folders not allowing access

I've had my MS surface pro for about a year. Love it. I don't have much on it, mainly Open Office and a couple of art / drawing programs. Yesterday I went to draw, and the One Drive wouldn't let me open the file. I found I couldn't copy folders or items in them and paste them elsewhere. Some investigation showed me that I do not have permission to access the folders. (One Drive couldnt access it's folder because of this). I tried changing permissions, but found that the options are all greyed out. I tried to run as administrator, but it wouldn't let me make changes like that either. It said I needed permission from the Administrator (computername). My name, Computername?Administrator and System all have the same permissions, but all are greyed out and will not let me change anything. I have spent hours troubleshooting and reviewing permissions/sharing, but nothing seems to be active.Any thoughts? Thanks in advance.

Is the hard drive full or nearly full, by chance? That will lead you to suddenly have permission errors, because Windows no longer has room to store the security information.

If you open C:\Users, does it list any folders besides your name, Default and Public?