ATT uverse receiver is showing a no signal error in TV..

no signal means your tv is on the wrong input

ATTHelp may wander by in the next 24 hours or so.  Until then...

The message you are getting is just "No Signal" not a full screen message with a lot of troubleshooting instructions?

Did you make sure the HDMI cable is firmly connected on both ends?

Did you power off the TV as well?

Are there any lights on the TV Receiver?  Which ones?

Do you have anything else connected to the TV that is working (e.g. FireTV Stick, Roku, Chromecast, BluRay/DVD Player)?

Hi, Thanks.. It was working on the same HDMI port 1 Input for last several years so I was certain it is not a HDMI cable or port connection issue.

GOOD NEWS is that Uverser receiver has started working on the same input/output HDMI TV port.. I tried re-seting the U-verse receiver box every 30 min and finally it started working in the same HDMI port 1 .

Not sure why the issue happened - I suspect some server issues in ATT Uverse complex.

Yes I do have other wifi devices like ROKU etc which is working fine in all the HDMI ports.. That is why I was certain that it cannot be the TV or HDMI cables ports/cables. 

I wish I knew why the problem occurred. 

I too am having the same issue with "no signal" showing on my TV from the main box. I have tried all solutions also and when the signal is gone, I see a blinking green light to the right of the power button. My wireless boxes are working fine, and I have no issues with the other TV's and programing. After waiting several minutes, the cable box resets itself and I see the "U-Verse logo" on the screen and the TV program resumes. After changing channels, it goes out again. 

I have been told U-Verse is not sold any longer and probably not supported anymore as a priority like the landlines. 

I agree it is not the TV or HDMI port as I can get other Wi-Fi Servies to work. I am going to try and reach out to someone by phone. 

@Hummerh306 , how is your receiver (that is acting up) connected to the gateway (Coax, Ethernet, Wi-Fi)?  Are any other boxes connected using the same mechanism?  

So far it sounds like a bad receiver.

I have a coax in to my Cisco “U-Verse”box then from there to my U-Verse TV receiver. HDMI cable to the TV.  It has been working fine until yesterday. 
my other receivers are wireless and only cable used is from that box to TV. I have unplugged power to all equipment and rebooted with same results. 
This morning programs come on then they go off then back on. This issue is only happening on the main wired receiver. 

By "main wired receiver" can we assume you are talking about the DVR?

Before you call and potentially replace the DVR try this: 

Unplug the DVR and the gateway.  Wait 30 seconds. 

Plug in the gateway FIRST.  Wait for ALL lights to come on.

Plug in the DVR next.  Wait for it to become functional.

Check to see if it's working correctly.

If rebooting doesn't work you can call and get a replacement DVR sent for a self-install.  You will lose your recordings but not your schedule.  You have 21 days to return the bad one via UPS/FedEx.  Keep the receipt.

after going through the trouble shooting at home I called support. Went through same procedures and even a software update Support is sending out a new box to replace the 5 year one. 
But, I turned back on TV and service came back up and so far good without any interruptions. 
Stranger things. 

Thanks skeeter for the suggestions and comments.