Hi,
I have a password protected file which sometimes appears to return a link-expired.txt error.
I updated WordPress and WPDM to the latest versions and after some testing I have found that:
Firefox on Mac = OK
Safari on Mac = OK
Chrome on Windows = ERROR
Explorer on Windows = OK
Edge on Windows = OK
Firefox on Android = was giving ERROR but appears to be fixed after the updates.
Any help would be much appreciated.