Screen won't display image after assembly replacement...

I smashed my iPhone 6 screen a few weeks ago, I then received an entire LCD assembly replacement with hope to get my iPhone working again [Previous screen was obliterated].

I'm confident in repairing iPhone 6 screens as I have successfully replaced the exact iPhone LCD twice and another two friends iPhones. However I'm stuck as to why my screen won't display an image.

After troubleshooting my phone over the past few days I have realised that upon charging my phone, it turns on but still no image. The phone vibrates with the mute switch and the classic iPhone wont unlock with TouchID after restarting. I've pulled apart the LCD multiple times and re-seated the cables on the pins. I can also see that there is a light when looking under the metal frame close to the home button.

The past LCD had bent/broken pins which explains why that never worked, but a full assembly replacement has got me confused.

Any assistance and or suggestions is much appreciated!

Thankyou