Easiest solution I've found:
Download a VPN extension for whatever browser you're using and turn it on.
For example, I use Firefox so I Googled "Firefox VPN" and I downloaded and added the first VPN extension I found (Browsec) and turned it on. Now my one drive files load without any problems.
Hope this helps someone because I searched for an answer for about 3 hours on what to do and found nothing useful. I eventually remembered using a VPN when I was in high school to get around the school's wifi filters so I thought to try it with this and it worked.