PIM372 always shows "No Signal"

Good day,

Received the display last week. I connected display and buttons to the driver board via the included ribbon cables.

Display powers on, crisp clean information dialogs. Shows HDMI and DVI options on display in the upper left hand corner, then switches to “No Signal” after a few seconds. Power off and on, repeat with different known-good cables and known-good video sources (RPi and computers) always “No Signal.”

Any suggestions?