Import PDF

I had been successfully importing/converting PDF scores for a few months.
Suddenly the process stop working.

I thought it would be a temporary glitch ... I normally use Firefox; so I tried MSN Edge...no change

After clicking on the file I want to import; the browser goes into a cycle of trying again and failing:
I get no error displayed

I assume that I have some setting which is not allowing the handshake with Musescore to pick up the PDF.

Please can you advise; I'm trying to learn to play the violin and Musescore has been a Godsend and I'm really missing the facility.

cheers

Fred