The oven safety valve or the pressure regulator has a shut off valve for the oven built in it. If anyone has done anything to the pressure regulator or oven safety valve, the shut off valve might be closed.
Check the ignitor inside the oven to see if it glows bright red when the oven is turned on. If the ignitor is red the oven controls are sending voltage to the ignitor and oven safety valve. Either the oven safety valve or the ignitor might be bad.
Someone needs to measure the voltage between the white wire on the oven safety valve and the yellow wire on the ignitor. The voltage should read 120 volts ac.
If 120 volts ac is being supplied to the ignitor and the oven safety valve and the ignitor is red someone needs to measure the amps drawn by the ignitor. The ignitor should draw 3.4-3.6 amps in order for the oven safety valve to open.
If the ignitor is drawing 3.4-3.6 amps and the oven safety valve is not opening, the oven safety valve is bad. If the ignitor is drawing less then 3.4 amps, the ignitor is bad.