iPhone 6 plus screen went static snow then died

I have an iPhone 6 plus of which I changed screen to a generic one bought from eBay about a month ago. It has been working quite good, though the new screen has at times been somewhat unresponsive, and there has been something that resembles a finger print slightly left below the center of the screen. When I pushed the screen, it kinda looked a bit like how I guess Harry Potter felt when Voldemort touched his head in the end of the Goblet of Fire, though not as visible. I have no idea wether this weak mark is relevant to this problem or not.

Anyhow: today, completely out of the blue, I took my phone out of my pocket and the screen had gone completely mad. It worked like a charm two minutes previously, but now just static snow, like an old TV with no signal. No response to touch or power button or anything. This lasted for a couple of minutes, then the phone died. Has been dead since.

I've tried to disconnect then reconnect the screen, and I also tried to reconnect the old broken screen, but still no response. Any ideas to what I could do?