I have the 2016 ST 270BH My cable is the one on the left. And like Tim said, " Switch antenna booster off to cable. Go to menu in tv. Select Cable, and scan channels. Should pop up"
Make sure your antenna booster is off.
On a side note, I have an HD antenna and when I was sitting in my driveway I scanned with antenna booster on and I was able to get 31 channels. Most were in HD. Crystal clear pictures. the 2 campgrounds I have been to so far, I got cable and the picture was standard definition, no HD. I should have unplugged and scanned with my HD antenna just to see if I got any. I'm still learning.
2014 Ram Big Horn CC 1500 tow package, 3.92 gears.
2016 Crossroads ST270BH (June 18, 2015)
(2015: 7 nights camping, 425 miles) (lost track and became too lazy to update!)