You did not state what camper you have so I will give it a shot based on limited information.
The amplifier switch is on the same panel that has you antenna connector and power receptacle. The green light should be off. If you have another wall plate with two connectors on it it should have a jumper connecting them.
__________________ Chuck - Sparta, TN
2012 Jay Flight 22FB, 2 x Honda EU2000i
2013 GMC Yukon XL Denali AWD
EDUCATION is what you get when you read the fine print.....
EXPERIENCE is what you get when you don't.
Yep, find the amp switch, make sure the light is off. Then you can use your remote to switch modes to cable.
Congratulations and enjoy getting to know your Precept.
Darrell
__________________ Darrell, Mary & K.C. Toller Mix
In our hearts: Goldens, Tess & Jericho
'15 Jayco Precept 31 UL "Bertha"
'13 Wrangler Sahara...AKAFUN
Roadmaster base plate
Ready Brute Elite towbar and brake combo
Darrell, Mary & K.C. Toller Mix 
Linear Mode
