Blank screen after screen replacement.

Hi, really hope someone can help me. I have read a lot of other questions relating to this on here but none quite the same (I don't think).

My screen smashed on my iPhone 6 so I have replaced it. I swapped all the parts to the new screen, plugged in all the connectors and turned it on to test it.

I must say at this point, I did not replace the shield yet so this can not be long screw damage.

The screen worked but the finger print scanner did not. So I popped the connectors off (I admit I forgot to power down first) disconnected to finger print scanner and reconnected. I plugged the screen back in and nothing, just blank.

The phone works, if I flip the silent switch it vibrates. I can hard reset to turn it off, turn it back on but the same. I have plugged the screen into another 6 and it works perfectly.

Any idea what to do/try?

I can't reset in iTunes as the passcode is on and the screen is blank!

Any help is appreciated.

Thanks in advance