I have a Panasonic TV having 4 HDMI inputs. When I use some other HDMI input for a moment and switch back to Tablo’s input, I often get a Black screen or garbled video and need to play with switching back and forth 2 or 3 times to get the Tablo’s image right again. Suspected the AUTO Resolution Select of the Tablo to be the culprit and fixed it to 1080p without success.
I have run across HDMI cables that just don’t work well. And when it happened I’d get the black screen when switching to the device using it. Usually sound with no video. I found that unplugging the cable from either end then plugging it back in would fix it. In the end I would get rid of any problem cables and replace them with good (but not expensive) new cables. Problem solved in every case. Try swapping a cable used for a different device, that is not having this problem, with your Tablo cable to see if it resolves it.
I still own and use some Panasonic LCD TV’s. In the U.S. Panasonic left the consumer products business and I’m not sure they have sold a new model TV in the U.S. since 2013.
I have a 2013 model and it seemed to have been the end of the models sold in the U.S.
Even reviewing the manual I couldn’t tell what version of HDMI it supports.
The Tablo HDMI specs indicate it has a HDMI 2.1 port.