iPhone 6 unresponsive after screen replacement

So, my IPHONE 6 was recently subject to a smashed digitiser. I purchased a new OEM digitiser/LCD full assembly from a very reputable supplier. After fully powering down the phone, disconnecting the battery, transferring the TOUCH ID/Home button and fitting the new screen I powered on the device to test it and all is well, the device works! Now everything works fine I push the whole screen into place (gently) and pop in the two lower screws to finish the job.

***Just to clarify that I did not mix up the screws, I am already aware of the long screw problem.

I now go to use the phone and the screen is black, I pressed the lock/unlock button to try and wake the device and its now unresponsive. I have tried a hard reset, new battery and testing the old screen, they all fail.

I have also plugged the device into my Macbook, iTunes doesn't detect the phone unless I activate DFU and start recovery mode. When I try to recover the phone through iTunes it downloads, extracts and starts the installation, however, it hangs on "waiting for phone" and throws back the error "iPhone could not be restored 4005"

I have now exhausted all my ideas. How can a phone be working normally and then not?

After putting the last two screws in the bottom it seems to have had a coronary.

Thanks in advance.