Is the battery fully charged?
You cannot turn on the camera when the battery level is low.
Charge the battery and retry.
Are you using the camera in a cold place?
The performance of the battery may decrease temporarily
when using in a cold place.
Warm the camera by putting it inside your jacket for a while
and retry.
Is the camera turned on?
Charging cannot be done when the camera is turned on.
Turn off the camera and retry.