I've tried turning on keyboard, light blinks twice and goes off. Batteries checked and OK. Keep getting above message, alternating with " Attempting to connect to keyboard#1". Mouse OK.
What else can I do?
The light shouldn't go out until it is paired. Do you have another set of batteries you can test with?
In System Preferences/Bluetooth is the keyboard showing as connected?
Apple support articles
Bluetooth Quick Assist
Retrieving data ...