Tuscany Navona shower with no cold water at all

My shower was installed a few years ago and just recently there has been no cold water in it. all other faucets work fine. I believe it is a Tuscany Navona. what do I do from here. There is cold water entering the faucet just none coming out.

If it is a pressure balanced valve, which is very likely, you probably have a stuck or defective balancing spool.