Does the light in the cabin come on telling it on? If so fuse ok. With bonnet up, engage ac, you should hear the compressor kik in. Most probably though yo be honest a dry joint on the new pipe, should put rubber grease on o rings to seal them properly. take it back to were you had work done, they will have to use a sniffer to find leak, not just vacume test ad vacume can seal any o seal leaks. hope that helps.