Having the same issues. Alexa app recognizes my STBs, I can pair with the Echo Dot in the same room. Alexa responds to voice cues as if channel changing commands are successful, but nothing actually happens.
My setup: Verizon Quantum Router acts as DHCP server and Default Gateway for my home subnet. I have a TP-LINK wireless router that is broadcasting my SSID, on which the Echo Dot resides.
Is it possible that the network traffic required to get from the Echo Dot (on WiFi) is not getting from the TP-LINK router to the Set Top Box (which is connected directly from the FiOS Quantum Router via coax)?
I will try getting a Verizon tech to hard reset my STBs when I get home tonight.
I highly doubt your TP-Link is an issue. I, like others, am using the Verizon router (although I also have the Verizon extender) and it's not functioning 100%.. I agree with a previous poster that it's probably on the Verizon end as a portion of the skill works (search, fast forward, etc.). I show 100% green in the Voice Control troubleshooter so I know it's not on my end.
I'm on hold to get a tech to reset to see if that works for me.
I did tweet to Verizon. First response was to "delete the skill, wait 15 minutes, then try again". That did nothing. I was able to search, ff, but no actual channel change.
I tweeted that info to Verizon. They responded "There is a known issue we are investigating. Issue should be resolved tomorrow morning. ^CAR"
So we'll see.