I mentioned this in a topic I just made, I have the exact same issue.
The thing is, it’s only like that for a few hours after upload, then the permalink fixes itself and normal users can visit the page and comment.
I have the File Page URL slug set and running “Fix File Pages” it reports back:
0 missing File Pages created. Fixed 0 File Pages with wrong post type. Removed 0 obsolete File Pages.
It’s always been this way, no idea why.