Quartus Prime project access permission error

I recently had some issues with the same error message- it occurred very suddenly in a project that had previously been fully functional. I have had some success re-creating the project in C:\workspace (the only folder on C I can write to) instead of "Documents".

I could not include any of the files from the Documents folder, I had to create new files and copy:paste the old file contents into them. Luckily it is a fairly small project and it was doable. I don't know why the error started and I am not thrilled with the workaround, but my work is no longer blocked.