Here is another thread with a similar issue:
Not sure it will provide a solution, but others are having similar issues.
I've just encountered this problem today, but the error message is slightly different
What's weird is that I was already using this project earlier today just fine, and everything saved fine. Double clicking from the file folder doesn't work for me
I am noticing " - " and spaces in the project location. I have a technical article which discusses the same problem, please try following this:
this hasn't happened on any new projects, but the one(s) where it does happen are basically toast.
luckily I exported layouts for the project to separate files and was able to rebuild. So now I keep updated copies of all Layouts and Maps in my project folders in case this happens again.
Save early, save often.
I'm getting this error ever since IT moved our network drive to a new location - I even built a new project in the new location and STILL get this error - I do not see anything still pointing to the old location. I have to browse to the aprx file in File Explorer and open it from there - very annoying!