I am getting this error today when attempting to open files through desktop browsers as well as via the mobile app. I have tried two different browsers on my laptop (Firefox 64.0 and Chrome 71.0.3578.98, then Firefox again after clearing full history/cache in safe mode), and also the mobile app on iphone. No dice.
I can't find a similar scenario in the help center here so I'm posting in the hopes that I can get something else to try!