Cannot get remote to connect to receiver

[mikeselectricstuff]

Any clues as to what could be going on here :
Bought a duet to replace a dead receiver.

Remote works with my existing second receiver, so definitely working.
New receiver's SSID appears on my laptop, so new receiver's wireless is working.
But I just cannot get the remote to see the new receiver whatever I do - have factory-reset everything.
(I do not have a wireless router - receiver is wired)

Remote firmware version is 7.7.1 r9557

[Soulkeeper]

I'll write an answer in this thread.