Receiver/DVR defective?

That doesn't look like any screen I've ever seen on a UVerseTV DVR. 

Do you have UverseTV or DirecTV?

@baseballisback   Any thought?

Its UverseTV

Can we see a picture of the receiver/DVR?

That's an odd one.

Model VIP1225 - its ~8 yrs old now

What kind of TV is it?

Samsung 65" Class - Q8 Series - 4K UHD QLED LCD TV

Today, I got the error message for the very first time while watching normal TV broadcasting.  This has never happened before.

What do you mean by normal TV broadcasting?

Normal Uverse TV, not a recording

@bbpanel8. Do you have the Owners Manual for the TV? 

I have to believe that the screen you're seeing is referring to an issue with the TV and not the DVR or your Uverse TV service.  I've had UverseTV for 14 years, have had numerous DVRs and STBs and have never encountered the issue you are describing.

I have reviewed all of the material that came with the TV.  The "owners manual" is a 4-page leaflet that is pretty much useless.

That message is generated by the Samsung TV, I think it's the equivalent of a "No Signal" message; i.e. the selected input isn't providing a signal.  Search Google for:

        Samsung "Check Device Power"

and you'll see pictures similar to your screen from Samsung TVs connected (or not) to a variety of devices.

When it appears, check with the TV's remote what TV input is selected; perhaps the TV has seen a stray signal on another input and has switched... but then found no signal.

Good point.

I'd be starting to investigate the TV as the cause of the issue.

Troubleshooting the HDMI cable via the TV settings says the cable is bad.  Don't know why its good one minute and bad the next but cables are cheap so I'll replace it tomorrow and see what happens.  I don't know the vintage of the cable I have so we'll see what happens.