Hotpoint SA2844HIX fan oven problem with temperature

Hi all

the issue I am having is this

I turn on the oven on fan assisted with both elements running it bleeps as normal and heats up, after this nothing happens, as in if I turn the temperature knob up it doesn’t call for heat, So doesn’t get hotter if I set the timer the oven gets to temp and then over the time the over is counting down it seems just to cool down. I have changed the thermostat, tested the elements all are fine, resistance all below 100 ohm’s so no apparent issues with them, one relay I tested seems to operate by supplying 12v to close the relay and allow 240v to pass to the element but if you turn it down it goes open and looses 12v so 240 switches off to element but if you turn temperature knob up again it does nothing, I feel the problem lies with the main PCB but cannot seem to find one except for a un programmed board.
If anyone can help it would be appreciated

Dave