Dear Terri Cheeseman,
Greetings! Thank you for posting in Microsoft Community.
I'm sorry you have issue with project filenames when using Microsoft Project.
I didn't reproduce the same issue when testing in Project desktop application. May I know the Version and Channel of your Project? I'd like to test in same version as yours.
Please go to File>Account, then capture a full screenshot of Product Information from the Account page.
Since you mentioned this issue happens in the last few days, may I know if there is anything change with Project? Does this issue happen after Project update?
We look forward to hearing from you; Please understand that our initial reply may not always immediately resolve the issue. However, with your help and more detailed information, we can work together to narrow down the situation and try to find a solution.
Thanks for your time and cooperation! We hope you have a nice day, stay safe and healthy.
Sincerely,
Tina | Microsoft Community Moderator