Chosen Solution
You should have followed the guide properly and or at least removed the screen. The slightest nudge can damage the cables. You could have damaged the battery connector but after installing the bracket your symptoms would point to the front top flex assembly. · Disconnect the front top flex assembly and see if it boots. · If it doesn’t, disconnect the home button flex so you are just left with the LCD flex connected. · When you find the one that’s faulty it will need to be replaced. If it is the home button flex you will need another screen. You might need to put the bracket on over the battery connector if you have disfigured it. If you have some sort of magnification and some tweezers you might be able to fix it up so the connector sits tight and flush.
