On our 2017 Cardinal, I experienced the same thing. Eventually I pulled the panel to see BEHIND the docking station area (where water, cable, satellite, etc. enter). I found a splitter back there but the problem was...the INPUT for the satellite was attached to one of the OUTPUT sides. I disconnected it and the cable that was attached to the INPUT and swapped them.
Instant fix - and five months later it's still working fine.
I can't help but wonder if someone did that just to cause grief - or perhaps it was lunch time, or a new employee, or who-knows-what, but that was a stupid mistake.
Robert & Estha Shiflet
Cardinal 3456RLX - '17 Ford F350 Lariat Ultimate - DRW w/B&W OEM Companion hitch
Nights Camping 2012 - 2020: 966 ~ Nights Camping 2021: 4