Time for a trip to the Genius Bar! If iTunes is not recognizing the device, then you're going to need some higher level help. Make an appointment and take it to the Genius Bar for diagnostics. Meanwhile, you can reinstall the various connectors that you may have to had removed in order to do maintenance, to see if an improper connection could have led to the failure of the built in start up test. (Most Apple devices will run a hardware test before booting the operating system, and if it fails this test, then iOS will not boot.) Hope this helps!