Solved!

I had to memorize the controls to enable automatic resolution while the steam deck was plugged in. Looks like the steam deck has a different settings profile for each display that I use. When I was messing with settings previously, I must have set a resolution that was incompatible with the tv. When I changed the setting on a (different) display that worked, the change didn’t effect my original tv. The tv wouldn’t work anymore with my deck, though, so I had to plug it in and go to reverse my change from memory.

Yeah, I had to memorize the controls to disable automatic resolution while the steam deck was plugged in.