When I try to open Dropbox files on my laptop, I get the following message:

When I try to select the document and grant permission, permission is denied. I am signed into my dropbox account and have tried downloading my files from the website; this also does not work properly. They download as "read only" and I get a message telling me that in order to edit I should create a duplicate of the file. When I try to do so, I get another error message.

What is going on here? I've used dropbox for 10 years and never seen anything like this.