Are you running on propane or butane?
Butane stops gassing at ~4c.
If you are on propane it could be the thermocouple that needs setting further into the flame or just your burner cleaning out.
The thermocouple is there to turn the gas off if the flame goes out.
Thanks folks, already been serviced. Apparently it is a problem with the control board. A new one is on order.(It kept thinking the flame had gone out and shutting the gas valve.