Corrupt Set Box

A few nights ago I attempted to change the input on my main yet older (Phillips)TV to use a ROKU stick.
I reached the home screen but it wasn't responding, so I turned on my other (Sony) TV and changed the input
to use a Firestick, the TV went black and since then I've been unable to power it back on. There's a switch
on the back of it that doesn't seem to work for me to power on manually.
I called AT&T tech support and they confirmed the problem is due to a corrupt set box. I just received the new one
and attempted to set up the TV.  I really had no great hopes for this to work without being able to power on
the TV on its own through a devoted outlet . Am I missing something?
I got the Phillips back to TV mode the other night and I've had no problems in the interim. Today I checked to see if I could use
my ROKU and the home screen was still frozen. I changed the batteries on the remote and that seemed to do the trick.
I suspect the fact I had issues with (2) TV's simultaneously may be coincidence. I don't know. 
So getting back to the setup for the new set box. The WAP sits by the Phillips TV along with the existing Gateway.
I connected the new set box/receiver with the same HDMI cable. From there as stated I was unable to power up the Sony TV.
By the way I dug out the TV remote and changed the batteries, it does not light up. I plugged the new receiver into my surge protector. I get 5 green bars and the yellow link button, then they go black. Eventually the link, HD and record buttons flash and then it just cycles through with no response from the TV. Is there something that AT&T has to reset? Any ideas what may have happened and why?
Is my TV dead?