The 5th burner, griddle valve had seized. Fine, I took it apart, greased it and now the valve will not turn. The knob turns fine. There is gas in the pilot light, but when you turn the knob, it's like the cylinder inside the valve does not turn. There is no tell tail sound of gas flowing through to the burner. I cleaned and greased all the other valves, and they are fine. I even compared the other automatic valve with this one to see if I missed anything, but it looks good. I haven't forced it. Any suggestions? Thanks!