Things to check:
1) Make sure the screen USB power cable is connected to the power bank and not the Pi
2) Is your HDMI cable plugged in all the way behind the screen? Sometimes finessing that cable will produce an image.
3) Isolate the problem by connecting the Pi to an external monitor or TV through the HDMI cable. You can alternatively try hooking up your cable box to the Piper screen.
5) If the image is still not working, and the Pi shows only a red light, you may have a defective Pi. Shoot me an email for a replacement ASAP at Tommy@withpiper.com and please provide your address.