Thanks for the advice. I'll give the low baud rate a go. I think I tried power off, wait, on and don't touch anything but will give that another go.

Puttying to the 561 does not give a response.

Re: Serial port on motherboard... I keep an old PC (windows 7, 32 bit) for just this sort of thing (also have an old citizen dive watch the comms software doesn't like W10x64). Even modern boards (I have an AM4 Ryzen 7 PC too) have a com header on the motherboard, a £2 bracket with a 9-pin d-sub on it fits in the back panel.

When you die the one with the most toys wins