He said he did the reset thing a couple times already but it probably wouldnt hurt to try again. There is one mistake that people make when doing the reset however and that is forgetting to turn off all three valves on the grill before reconnecting the LP tank. If you open the tank with the valves open, it will sense that as a major leak and again trip the safety check valve.
So, turn off all burners, close the tank, disconnect the tank. Wait a minute or two, reconnect the tank, then ensure the grill valves are still OFF and Slllloooowwwllllyyy open the lp tank valve. Once you get it open a couple full turns, you can open it up the rest of the way normally. Then turn on the front burner valve and light the grill, then turn on the back burner. If you don't get good flames, then concentrate on the regulator on the hose.