Get a set of removal tools for the head unit, pull it out and re-seat all the connectors.
If this is not a 'base' model, pull back the carpet on the passenger side and you will see a white metal frame held in place by 2 10 MM nuts.
Remove the nuts and fold it down, re-seat all the connectors on the large module ( this is the amp, the other one is the TCC if you have an automatic transmission )

Hope this helps.