Hi . the jet may be blocked , check that no food has dropped onto the burner. The first thing to do is remove the burner and clean it thoroughly making sure the jet where the gas comes out is clean and clear. Put a hoover on it if you can .
Also check the bypass within the oven thermostat is not blocked .
tried that please note direct ignition no piolot
Have you cleaned the bypass?
There will be a bypass screw that can be adjusted/ removed