Solved: I don’t know which of these fixed it, but I did all three and it works now. Took TX to the garage and using an air compressor, blew air through all of the vents/grills. Lots of dust. Compressed air can have a lot of moisture if you live where it is humid, so be careful. If you don’t have a drier on your compressor, maybe use canned compressed air designed for electronics. Gently laid the TV over on its face (protected with towels) and lightly tapped on the back in several places. Finally, with it plugged in, I held down the power button for 30 seconds. Seemed to have worked. Also, plugged it directly into the outlet and avoided the power strip.