It may be in "hibernation mode"
Connect the battery to the charger.
Wait for 5 minutes.
Disconnect the battery.
Press the power button for 3 seconds, then release it and press again for 20 seconds.
Reconnect the battery to the charger, and it...
I don't know why you imagine that photo work won't require 3 batteries - you would be glad you had them if you went that way, but not as pleased as you would be with the creative combo that means it doesn't matter if you forget the SD card !
And...