The toggle switch is for the illuminated reticle. Up in "on", down is "off".
The battery compartment is on the same side of the scope, but rearward and has the knurling on the cap. It may or may not take a conventional battery of some sort. Also the bulb could be out. The switch could be bad. The system does not generate much light, it could be working fine and not visible in regular light. But...they get left on regularly.
Kalinka Optics may likely have parts if you need them. They also have a pretty good tutorial (well sort of) on the scope, zeroing same so the bullet drop system is claibrated, ranging system and light troubleshooting.
You have a very unique rifle.