Why does my phone stays its logo if I open it

If you have access to a computer or laptop you can download the Sony PC Companion Software from the Sony website & use it to restore the firmware of on your Sony Xperia J....

Another way to reset the firmware is doing a factory reset via the recovery menu. Execute the appropriate button combination to boot the phone into recovery mode & then choose "wipe/factory reset" option.

This method will completely erase all your files on the phone so make sure you've backed up anything important prior to resetting it

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