Why does the a/c not work on 2012 Chevy equinox, when turned on.

It's very possible the freon is low. That is about 50% of all AC issues but it can mean there is a leak in the system. I would suggest bringing in to a shop that can check the level, install a dye and check for leaks. If you don't work on your own cars then use this link to find a good shop near you. https://repairpal.com/repair-shops Alex