New screens - Screen turns on but black? (WORKED BEFORE)

Hi,

I have bought some new screens.

I tested them, all 3 working but 1 had death pixels..

So after some time (now) I tested them again and now they don't work anymore?

They turn on but give a black screen? It is not the same black as it is off, but still black.

What could be the problem for this?

I have 1 working screen, with that I can see that the phone works perfectly?!?

I haven't put pressure or something on the new screens so I don't think I damaged them?

Maybe I have bent the connectors of the lcd? Could that be a problem?

Does anyone know the answer?

Thanks!