If you have the fan setting on your thermostat set to “on” or “run”, causing it to run all the time, it may just be that the compressor has cycled off and there is nothing wrong. You can try adjusting the thermostat down and see if the air conditioner kicks on.

The other option is that something is not broken and it needs to be diagnosed to figure out what is causing the problem. It could be a lot of different things; frozen coils, refrigerant, bad compressor, a capacitor that has gone out, etc.