iPhone 7 is Boot Looping after Housing Replacement

I have just replaced my iPhones housing, lcd/digitizer screen, battery, main speaker and rear camera. Before the repair, the phone would turn on and work normally (apart from the damaged parts).

I have just finished the repair and the iPhone turns on and enters into a boot loop. It is not being recognised by a usb cable and doesn’t charge either.

When I disconnect the lightning connector assembly the phone turns on and works perfectly. I have looked for damage on the connectors and ribbon cables and I couldn’t really see anything major . I have now ordered an OEM replacement.

The only damage I could see are little dents on the ribbon cable. If somebody could have a look at these photos and give me some feedback on what the problem could be, that would be amazing.

I have not yet checked under the circuit board, so could be a problem there too.