2010 Tahoe LTZ A/C light flashes. Have pressure in the lines.

[Jrschultz]

Hello everyone. I took it in to a shop for a recharge seeing I wasnt having luck with the do it yourself cans at Advanced Auto. I worked good for a little while but then nothing. Light flashes 3 times and I get no A/C. Tok it back to them and they said they would need it for a while to diagnose because it sounds like something more electrical, but I didnt have the time and live a ways away. I did pull the cap off the line and I do have pressure. I am hearing about the Ambient Air Temp Sensor? Could this be my electrical problem?