A/C clutch not engaging

A/C clutch not engaging. If this is covered in another post, please direct me there. I cannot find it. I am quite sure my system is charged with refrigerant per a pressure gauge put on the low side. I swapped that A/C relay with another and also the diode. No difference. With the A/C controls on, the relay clicks when I plug it in and unplug it. Doesn't this mean that everything is good to go to send power to the clutch to engage it

If you can get to the a/c clutch check for voltage there.