I recently installed a nest thermostat for our AC system. Unfortunately I was short sighted and just assumed all the wires were the color I needed. Since installing the thermostat our system won’t cool. The fan runs and the unit outside runs but no cold air. The pictures show the wiring on out unit in the attic and how it’s wired into the nest. I’m confused why one wire says heat even thought this is AC only. Did I mess up the wiring or is it something else (low on Freon/bad compressor)? Thanks for your help!