2008 Chevrolet TrailBlazer temp gauge and AC don’t work

The temperature gauge stop working and a/c won’t work I already changed thermostat and temperature sensor and gauge still not working

Did you test the replacement thermostat in a pan of hot water to make sure it opens and closes with the correct dimensions and at the correct temperature? Did you measure the resistance of the temperature sensor vs temperature? Once you’ve verified both of those, then you’ll have to test the gauge itself. Probably a good idea to use one of those infra-red laser-spot thermometers aimed at the upper radiator hose as a way to verify the coolant is actually at the expected temperature, and the problem is the gauge or the wiring to it.

You’ve check the fuses, right?