All newer grill models have an excess flow safety device which kicked
in on your grill. The instructions are very explicit about the startup
procedure to keep from tripping the shutoff. If it happens, just shut
off the operating valves, then shut off the tank valve and open it
slowly to pressurize the system before opening the valve to light it.
The excess flow safety valve is usually a steel ball held by a magnet
in the tank valve body. A sudden spurt of gas will cause it to pull off
of the magnet and slam into the port. A small bypass allows some gas to
flow until the pressure equalizes and the magnetic ball resets itself.
Bon Apetit! Bugs