Electricity went out in my block for several hours. After it was restored, my thermostat Shows "bat-low". Put new 2 AA batteries but still shows "bat-low". Bought more new batteries, still shows same. Unable to change temp from 63 to 68. During early morning, my unit started running because it got down to 60.
Any suggestions? Thank you

Check your breaker, and reset your thermostat. Here are a few methods.

https://www.hunker.com/12406507/how-...ble-thermostat

https://www.hunker.com/12002099/how-...ble-thermostat

(The second method in this link says cut the main power for a few seconds)

You did shut it off before changing the batteries didn't you?