All I could do is guess - sorry. If it **was** working at one time and now is not working, then odds are one of the RCA connections has worked it's way out. But that's odd too as they are pretty tight. Let's hope it's not a broken or frayed cable.
If it's a connection, then your best bet may be to call Jayco and ask them to send a "TV/Cable" schematic. It **might** tell you where the connections are. I know mine are buried in the walls.
You're sure it's not the TV? You've tested those inputs on the TV with another source?
2016 Greyhawk 31FK