markovol,
sorry if I'm stating the obvious.

If I understand correctly, you have 2 switches. A rocker switch on the FP and a wall switch. If thats the case then they should be wired in parallel.
So when the rocker switch is in the 'off' position, the fireplace can be turned On/Off from the wall switch.

I have a similar switch on my gas stove. I leave the switch on the stove 'off' all the time. My stove is controlled via a wall thermostat.

Not so obvious I guess.

Mine is the same and low and behold when I turned off the switch to the gas valve and then turned on the wall switch it worked!

Thanks so much jasper for helping me with the obvious!

Glad I could help.
Thanks for the update.
-jasper

Wow. So glad I stumbled on to this old post. My fireplace is the same. When re-lighting the pilot this winter I flipped the rocker switch to On (thinking that was something I needed to do), and then was unable to turn off the fireplace from the wall switch. Flipping the rocker to Off allowed me to control the fireplace at the wall switch. Thanks!!!

My issue is a little more obscure - I can use the wall switch, but the flame goes in and out intermittently. If I use the rocker switch, the flame stays lit continuously with no issue. I had a fireplace maintenance company come out and service the unit and found nothing wrong ($300 service call). Any suggestions? Thank you!

Same problem.....anxious to see if someone has a solution

That might due to the corrosion in the switch. Try clean out the switch contact or buy a new switch.

Thank you, David - I replaced the switch and still persists. Any other suggestions? Much appreciated!!!