Fixing an old gas fireplace. Pilot flame lights but nothing else?

Does anyone know why my fire place isn’t working? I even cleaned out and added some D batteries to this mystery battery pack. Not sure what it’s for.

There’s no switch I can see anywhere that would allow me to turn the gas input from pilot to anything else like I’ve seen some tutorials online.

It’s a heat & glow 6000G-IPI.

Again, pilot flame works.. I can crank up the gas from lo-hi with that silver knob, but i can’t get the whole system to flame up.