Sounds faulty to me. The 3 year warranty has expired. You will simply have to replace it.
I turned on my Lenovo Y720 but the display showed "no HDMI signal from your device". I tried another HDMI cable, didn't work. I tried connecting to MacBook, same problem. I found a "solution in Dell forum" which said to disconnect all the cables, hold the power button 10 seconds, then doing the built-in diagnostics and connecting to laptop. Didn't work either.It worked well in past 7 days, before that I had a problem, it showed only black screen. I fixed it with the same steps, but looks like it is not working now. Also when I am writing about this the P2219H turned on with extended screen 2-3 times, but lasted for less than 1 second. What should I do?
P2219H, no HDMI signal from two PC