Hello, I hope the following is of assistance.
If there has been a leak in the air con. system and the refrigerant level is too low then the engine management won't allow the compressor clutch to engage. Also if the cooling fan is inoperative this is detected by the engine management and again the compressor clutch won't engage.
The cooling fan failing is quite a common concerns especially on the diesel engined Cmax. With the engine running and the air con. turned on check the wiring to the compressor, there should be a 12 volt feed and an earth, if these are OK then the clutch itself is at fault.
Start with checking if there is enough refrigerant in the system and that the radiator cooling fan operates and go from there.
Let me know if I can assist further or if you have more questions regarding this and I'll reply as soon as I'm able to.