Canon T3 / 1100D Will not turn on

Hi there, my usb connection broke off the motherboard of my camera 2 months after I purchased it brand new. I am a laptop technician so fully understand about forcing connections etc. The shop I took it back to said I would be forced to pay for the fix as they said it was obviously forced as they don't just break off! Not matter how much I argued they refused to take it under warranty unless I paid which would cost me more than the camera did! So I left the shop. Obviously the danger of a lose piece of metal rattling around inside my camera did not make me happy. So I decided to find a disassembly guide and open the camera to retireve the offending piece of metal.

On reassembling my camera I came across a problem. The ribbon cable labeled 'H' in the pic below would not stay put and kept popping the black hinged part. It will not lock in at all.

What is this ribbon cable for?

2. I reassembled the camera (stuck down the cable with a small piece of tape. All done, camera would not turn on. Pulled it all apart again, reseated all the ribbon cables, reassembled the camera, turned it on and it started! Yay. But said NO CARD. But it was on. I could sort it out later. Tried to take a pic. Error 20! Turned off camera. Removed battery, reinserted battery, tried to take a pic Error 20! Tried it with a lens, without a lens, on a different setting. Same Error 20 every time. Thought I have obviously missed something.

With great reluctance I reopened the camera, took it all apart again, tried really hard to check the card reader for the microswitch but really struggled to see it. So failing to find the microswitch I followed the process to the letter to reassemble step by step. Turned on and NOTHING!!!!

Also can you tell me if the black wire/cable between ribbon cable 'I' and 'F' is meant to be secured as it just slips into the connector but does not feel secure. I believe it is the fibre optic cable???

I simply cannot afford to send it in. I am trained laptop tech (not employed at the moment) so understand about working in an antistatic environment, removing the battery before working on anything. Very very careful to map screws and check cables etc before removing anything. I have to admit defeat here. Can anyone help me out? I am devastated as I cannot afford to take it in to a tech. Camera is literally a few months old and hasn't had much use so don't think it's dust or dirt. ANY help would be appreciated.