I have had the same problem and took the TV out and replaced it with another TVI had. However, I began doing some thinking and thought, perhaps there is malware or a virus within the smart TV. I reconfigured it back to factory settings and connected everything and it seemed to be ok an then again the popup. Thinking again, I thought-perhaps the FireTV Cube had a virus so I restored that to factory settings and so far the popup hasn’t returned. Perhaps if you have a streaming setup that could be the source of the popup?