I have tried to put a piece of card through the printer in the ordinary way, first by itself and then on top of a fill of paper, but I have had no success either way.
When you say "put a piece of card through the printer", do you mean in the ordinary way, with the printer drawing the card through itself, or do you mean pushing the card manually? If you mean the latter, I do not know how to do it.
Sorry for the delay in replying to your most recent Answer. I had to break off to have lunch and to collect my wife from her training course.
Before breaking off, I disconnected the printer from the power, and then opened it, turned it upside down and shook it to try to dislodge any paper that might have been stuck inside it. As far as I could see, nothing fell out of it. Unfortunately, my grip on it slipped and it broke apart, but I think I have successfully put it together again! I hoped that the accidental breaking apart might have cured its apparently false indication of a PAPER JAM, but it is still showing a PAPER JAM.
What do you suggest next?