Roof Antenna Problem:
1) What kind do you have? (Winegard Sensar "Bat Wing" most common)
2) All new digital TV is "directional" (Are you pointed at the TV tower's location?) The bat wings are like the wings of a plane and the white amp housing is the cockpit. Point the cockpit at the TV towers. Use a program like www.antennaweb.org
if you have Internet (there are others) or a smartphone app like "TV TOWERS" for iPhone (Best out there) as it has a compass built into the arrow that points to the towers. You just turn your body till the little arrow is correctly pointed and make sure the white housing is facing the same way you are.
3) Coax connections AT the antenna amp solid? (The white plastic box at the top with the wings sticking out)
WALLPLATE Power supply and switcher Problem:
Incorrectly called "the amp" it is actually a power supply FOR the amp located on the roof. It is also a powered switcher for the roof antenna or outside cable.
LED "ON" :
1) Power to the power supply - check
2) Power up to the roof amp to work the roof antenna
3) Roof antenna selected
1) power to roof antenna off
2) Roof Antenna DISCONNECTED and outside Cable Connected to the camper's COAX system
(See attached manual)
There is a SINGLE TV cable connection on the back of that switch that goes to a splitter. (there is also a different one on the face plate as well)
That splitter feeds your entire camper. A loose connection back there will affect all TV's in the camper but not the faceplate one.
Too far away from TV stations:
Once you are pointed AT the tower, it may be too far away to get a digital signal. Most (not all) Digital and high def TV signals are in the UHF band. You will need an antenna "focus" attachment to the older non-directional Sensar antennas. Called a "Wingman" for clever and obvious reasons, it works GREAT.