2003 Audi A6 1.9 TDI

Hi following on from my previous thread I am trying to establish if my compressor is dead after the car has not been used for a few months. The aircon is charged up and the HVAC head unit seems to work as it should with aircon cooling fan coming on when aircon engaged but the compressor doesn't seem to be comprising. I think its the constant rotating type with an N280 regulator valve that is electronically controlled (no clutch). I have checked the power supply which is good but it doesn't seem to activate the valve. I presume the valve is stuck as the car has not been used - I've tried a little percussion next to the valve but no joy.

Any way of forcing it into life before I go for a new compressor?

Thanks in advance