Okay… now don’t laugh… The wiring is correct. The software is correct. But I just found out that in my old set-up I had reversed the lines for the sender and receiver pins like this:
“transmitterPin”: 1,
“receiverPin”: 0,
so when I copied in my old config and followed the instructions here I changed these numbers to this:
“transmitterPin”: 17,
“receiverPin”: 18,
which is the wrong way around.
I feel really silly now. Everything is working now! Thank you very much for your help!