A1314 Magic Keyboard dead after battery change

[DCBassman]

Hope this is something trivial, because it's really annoying. I've been running this on Eneloop rechargeables, and all has been fine, until today. Put a fresh set in - nowt. Tried different sets and even types, but nothing.
Do they just die like that?

 

[DCBassman]

Apologies, I must be tired. I've just spent two hours messing with this keyboard (working perfectly now!), and I kept repeatedly, as I now realise, putting the batteries in backwards...
What can I say, d'oh...
🙃