Replaced lcd but here is what happended

Hello.

I have an iPhone 6 with digitizer issues, so when I got the new replacement screen, I moved all the small parts from the old lcd to the new one,(i tested the new lcd before moving the parts)but here is what happended,the phone was working with all the screws in their place I just haven't locked completely the new lcd into the phone,so when I pressed the power button in order to shut down the phone and lock the new lcd, while the phone was in shut down process, I tried slowly to lock the upper part of the replacement screen and suddenly a few lines came up and the phone shut down.Now when I power up the phone, it shows the apple logo for 2-3 seconds and then the screen goes black and after a few more seconds (12-15) the phone shuts down on its own. I tried the old lcd and does the same only difference with the old lcd is that after the short apple logo when the screen goes black it also shows very few lines at bottom left.

I used both screens in another iPhone 6 and they work.

I have done several iPhone fixes in the past all without any issues.

So plz tell me what went wrong and if there is any way to make the device work?

I have never seen this kind of issue before and I also checked the lcd connectors with microscope and they are not damaged.

Thank you in advance.