Battery indicator is very unreliable, so you can’t go off that. It is a very simple test to confirm if it is batteries or not. Put some new lithium batteries in, and if it works, it was the batteries. If you don’t have any, you may as well get some, because you will need them at some point, and if it isn’t the batteries, so you don’t need to use the new ones for a long time, don’t worry, they have around a twenty year shelf life.
Blink will only ask you to do that first anyway, so you may as well before you log a support ticket.