1996 town and country A/C

I have a 1996 Chrysler Town and Country LXi. About a year ago my wife took the van to get the radiator replaced. The air worked fine befor but has not worked since the radiator replacement. I have exahusted all efforts to get the shop that did the work to make the repairs. I checked the button in dash and wires and fuses and relays all are fine and taking it tomorrow to get pressure tested what should I look for if there is no pressure, what is the possibility the return lines are al hooked up wrong? Thankyou.