Magic keyboard stopped working

I've had a magic keyboard for just over a year. I took it off its lightning cable plugged into my keyboard, took my keyboard to another office to use with my AppleAir laptop and it worked fine. When I brought it back home, it would not pair with my IMac. I used the lightning cable, and even retried to pair it with laptop.

No luck! Darn, am I going to have to spend another $199 for a second keyboard. Makes me furious that the battery cannot be replaced.