AC not working?
First, check the batteries in your thermostat.
Next Check your electrical panel breaker.
Air conditioning is running but not cooling!
Check your furnace filter.
Make sure you Don't see ice build up on any lines inside or outside.
keep most vents open.
Is the fan blowing air?
If not,make sure the furnace power switch has not been accidentally turned off or bumped.
Remember the furnace switch often looks like your light switches, and the furnace and Air Conditioner work together!
If these basics have been checked, and its still not working, you most likely need a service call to your home.