Hoover DNH D913A2C-80 PCB help

Hi
I have a hoover heat pump dryer which is not switching the compressor on when starting a programme, I have checked over the circuit board and there is nothing obvious that I can see wrong with it. The compressor starts and runs if you activate the relay with voltage, but it isn’t being activated by the circuit. Has anyone experienced this fault and been able to pinpoint the faulty part of the circuit, or someone may have a circuit diagram so I can trace the fault easier. I don’t want to pay out £100 for a new board if its just a component that cost pence to replace. any help appreciated