Is the gas valve that feeds the appliance open all the way, or the flex pipe is kinked.

Do the other burners that work on this device?. If yes then the above advise is is not the problem.

The other issue could be the controller is not sencing that the flame is lit so it closes the electronic valve.

It may need a clean or something blocking the gas flow on that burner it could be a spider web or a ant inside the orifice