Are there any things I can check before calling a pro to look at my ac unit. I just noticed that my ac won't turn on. The fan works and the thermostat is reading the correct temp. I turned off the fan and turned the temp down to try and kick the unit on. Nothing happened. Could this be a thermostat issue? What else can I check?

You are saying the fan works,, are you talking about the fan than blows air (hot or cold) into you home?
If nothing about the a/c is working 1st check the breaker, it will be a double pole ,some units also have a breaker outside at the a/c unit,
It would help to know what kind of system you have is it a split system with a furnace/airhandler inside and a condenser outside
Let us know