Lopi Berkshire burner shuts off- pilot stays lit

Have Lopi Berkshire for about 5 seasons. Like it but for the past 2 years I've been dealing with the burner just shutting off on me. The pilot has always stayed lit. If I turn off it will relight but will make a quick flash and then start as it used to by flame moving from back to front much slower.
Talked to dealers and tried the following: Replaced the thermopile, replaced the thermo couple, cleaned pilot with compressed air can, removed burner and cleaned with vacuum. I do not have a thermostat on it.
About 2 years ago, I switched from 2 100 gal above ground tanks and burried a 500 gal tank. My gas provider performed the work and hook up. Not sure but think the issue may have started the season after this. They mounted some kind of regulator looking thing on my outside wall which then feeds the heater and my cookstove/ oven. Could it be something with that? Any help would be greatly appreciated. The stove was professionally installed and seemed to work well for a couple years. Although the installer was a crook (long story) I will never call him back.

No I didn't pull the orifice. Just compressed air to orifice. It says in my manual to apply thread sealant to orifice. What is used for that when I reassemble?

Removed burner and orifice today. blew out with compressed air can. Didn't see anything but blew it well. Fired up but went out twice after about 20 minutes of burning. Thought we had it. Any other sugestions would be appreciated, thanks

try by passing the switch.

sounds good but- I'm a novice, how do i do that?

valve has 3 screws on it.....top , middle and bottom........ connect the top screw to the bottom screw.....and now the main burner should come on and stay on.
id that works and it doesnt shut off then you know your wire or switch is bad.

before you said you replaced your thermo couple....but you said your pilot stays lite, therefore you did NOT need to replace the thermo couple. just saying.

you can use a wire or a paper clip to make the connection.

thanks will try tomorrow and let you know