Pull the two wire electrical connector off the compressor and see if you have 12v there. If you do the clutch coil could be bad, or the air gap on the clutch could be too wide. Also,some models have a sensor that shuts down the compressor if it's speed isn't where it needs to be so the serpentine belt doesn't get fried. There might be a fusible link involved as well. Without knowing the model/year, it's just thinking out loud.
If you don't, we need to look at the past. Did it work before you changed the Klima, and fuse?