Unable to publish for LMS do to 'Proper Security Permissions'

I just had this happen to me. That same warning message appears if I try to publish a file that I copied to my laptop yesterday. However, I tested a few other files, and I can publish those.

• I tried moving the unpublishable file to another folder. Still wouldn't publish.
• I tried saving a copy and trying to publish that. The copy wouldn't publish either.
• I tried quitting and relaunching SL. Still wouldn't publish. 

I'm going to submit a case (https://articulate.com/support/contact/360-teams ).

Update: I got error messages when I tried to attach my SL file to the case. I couldn't attach the image of the message, either. So here's the message I see when trying to publish, and the SL file is attached.

Another update: When I submitted the case, I got the following message

Thus, I don't know if all the info I provided got through or not.

The important note is this: The Storyline error message mentions the folder by name. But it's not showing the name of the selected folder. It's showing the Title in the project.