Here's my PC98 config: https://pastebin.com/GNisWHPH
3rd line from the config says:
ai_service_enable = false
So the translation service is disabled.
This is why I said I'd look tomorrow, I knew I would have done something stupid.
In my defence, my daughter is sleeping poorly so I am not at 100% over here.
I need to work out if I need to enable this for each system then, surely if the global settings are being overridden by this false line on each individual system setting then I need to edit each system config that I want to use. Don't answer that! I'll work it out.
Thanks very much, @mitu !
Edit: I haven't worked out the global/individual system issue yet, but I have this working on PC98. Clever stuff!