This video shows how to repair and reinstall the software of an unresponsive (“dead”) device, thus making it possible to use it again.
Note! The Xperia device should be charged to at least 80% and the computer should be connected to a power source before you perform a software repair.
A software repair can be used if you experience critical performance issues, if you can’t start your device even though it’s fully charged, or if you have forgotten your screen lock password, pattern or PIN code.
Make sure that you know your Google™ account username and password before you perform a software repair. Remember that all user data on the internal memory of your device will be deleted, including downloaded apps, photos, and device settings. Content on the SD card will not be deleted.