Well it’s working now anyway! Something got updated – I didn’t see what, I clicked through too quickly. Looks like Download Monitor had a new version today anyway. Now in Download Monitor there’s a tick box in the Quick Edit area for Members Only, which worked once I had unticked and re-ticked for all my downloads. (I suppose it’s possible that it was there all the time and I didn’t see it – embarrassing for me if so!).
Thank you for your reply @mbrsolution, I would have tried both of your suggestions, but as it is – case closed.
Thank you.