I had to cut the tabs off at the LCD cable end connectors, and flip them around. Both cables had to be flipped around. Then it came to life. I use the RAMBO 1.4, and the keyed tabs at the board were fine the way they’re supposed to be installed. As someone said to me, there’s only 4 combos you can try, one of the 4 will be the right one lol
I should mention, this was exactly what it did to me when I was building mine. And here’s the thread with the answer to the problem I was having. Look around 12 days ago.