Screen turning on and off after replacement

Hi,

I have replaced the whole screen and frame on my P9 Lite. The phone turns on, however the screen flicks on and off. It's perhaps 1sec between each flicker.

I have tried re-connecting the original screen and although the LCD has cracked, it does show a few lines of colour and these lines stay on continuously - no flicker.

Does this mean the screen I have received is faulty? or is there something I can try?

Many thanks,

Andy