Replaced LCD and Screen and now screen wont turn on

I have recently replaced both the screen and LCD on my iPad Mini 2, now the screen doesn't work. I know the LCD is fine because, I have managed to get the apple sign to appear around 5 times but then it goes off again pretty much straight away.. I have tried hard rest, restoring the iPad, unplugging the battery for 10 minutes. Is there any thing else I could do or will the battery need replacing?

Thank you in advance