Sounds like either no power to the compressor or a bad compressor/clutch. First thing I would do is check the connector. Make sure it is connected, not knocked loose when working on something else. I did this one day on the Merc. My wife complained for couple days that the ac wasn't working before I got too it. I fixed it by putting the plug back on, but I sure didn't tell her that it was my fault to begin with.

The plug could be attached, but not making good contact. Check for corrosion, broken clip inside connector, dirt etc. Then I would check the voltage of the turn on lead. If you aren't sending a signal when you hit the switch inside it won't kick the clutch to turn the compressor on. If you are getting power to the compressor, then I would guess that it is the compressor itself. I think you can jumper 12 volts directly to the compressor to test if the clutch engages, but if there is power at the turn on lead it is probably a moot point.