Something you should check, if you have any other
Bluetooth devices, is to see if they show up on the Mini.
This will atleast indicate that the Bluetooth radio in the
Mini is functioning.
If the Bluetooth radio in the Mini appears to be working,
then it may be that the keyboard has bit the dust.
Also, do you have anyway to check the batteries? It is
possible one of them may be bad. It is highly unlikely but
it does happen on rare occasions.
FWIW, I have a couple Apple wireless magic mice, an Apple
wireless keyboard, and an Apple wireless trackpad and all
have been working just fine for a few years now.