Is this propane or natural gas? Standing pilot?
Fuel supply first.
Second, perhaps the proof of pilot flame is not registering. Some use the small cylindrical rod with a single wire lead, if so, pull the sensor and rub it with a scotch-brite pad, nothing metallic.
Perhaps the gas valve itself is the problem?
Look at the source of ignition.
Sorry to be so sparse, but I am not there to see for myself...