Hi Matt The issue occured because you must of damaged one of the key componets which allows the screen to turn on , the ram might installed incorrecly so please try to re-insert and see if does work and if doesn’t its a hardware fault.
Hi Uninstall iTunes and reinstall from Apple direct website https://www.apple.com/uk/itunes/download...-you/ and step 2 use a different lighting cable . And it should fix it and if it doesn't work it's a problem with your device
Hi J Sam Your problem sounds like an antenna fault which can be cheaply replaced by Apple or a Phone repair shop and after the repair the phone will work Thank you for co-operation John IT Troubleshooting Team
Dear 막내쯔위 @maknaeyoda It looks like your LCD was’t installed correctly or is faulty part and The fan probably got damaged while cleaning i recommend taking it to the shop where you have taken it and getting it replaced with a New LCD and repair the fan or refund as they work should come with warranty by law