I have followed the directions to the letter (choosing my provider and logging in, choosing the specific TV, linking the device) get the Echo Show to turn on the TV. I have three TVs and each one is identified by a Genie with a specific number. Alexa repeatedly says she can't "turn on the TV." I called Amazon support and they were less than helpful because they told me to call DirecTV which was also useless.
I have read earlier posts with people having a similar problem but they were using a third party device as the bridge between the Alexa app and their Echo, Show or Dot.
Very frustrating to say the least.