[PROBLEM] Blank screen post one time successful boot on pi3

[Dave400]

I have already tried the shift key trick..

1: Staging repo
2: Estuary skin on the Krypton build
3: Although specified otherwise those were the default values when I first built up the pi2, values have been commented out now, no change
4: It was originally pi2, the last update was applied via that device, i took the card, placed it in the pi3 and it booted fine whilst connected to one of my monitors, eventually shut it down (via on screen menu) plugged it into my main tv, booted and nothing. Since then have put the card back in the pi 2, doesn't boot. connected both devices to my monitor, still no boot. stick a card (same capacity) with a different product on (Retropie) on both pi2 and pi3 and they boot fine.