Have you tried this?

Your device may fail to restart if the battery level is low. Connect your device to a charger and try restarting again.

1. Long press the power key.
2. In the menu that opens, tap Restart. The device restarts automatically.

1. Long press the power key and the volume up key at the same time until your device vibrates.
2. Depending on whether you wish to force the device to restart or shut down, proceed as follows.

• If you wish to force restart the device: Release the keys at this point. The device restarts.
• If you wish to force shut down the device: Continue pressing the keys. After a few more seconds, the device vibrates 3 times and turns off.

To avoid permanent damage to your device, do not interrupt a factory data reset procedure.

1. Back up any important data that is saved on the internal memory of your device to a memory card or other non-internal memory. If you have any encrypted files stored on an SD card, you should also remove the encryption to ensure you can still access them after the reset.
2. Find and tap Settings → System → Reset options. You may find the item under Advanced.
3. Tap Erase all data (factory reset) → Erase all data.
4. If required, draw your screen unlock pattern or enter your screen unlock password or PIN to continue.
5. To confirm, tap Erase all data.

Your device does not revert to an earlier software version of Android when you perform a factory data reset.

To avoid permanent damage to your device, do not interrupt a factory data reset procedure.

1. Back up any important data that is saved on the internal memory of your device to a memory card or other non-internal memory. If you have any encrypted files stored on an SD card, you should also remove the encryption to ensure you can still access them after the reset.
2. Find and tap Settings → System → Reset options. You may find the item under Advanced.
3. Tap Erase all data (factory reset) → Reset phone.
4. If required, draw your screen unlock pattern or enter your screen unlock password or PIN to continue.
5. To confirm, tap Erase everything.

Your device does not revert to an earlier software version of Android when you perform a factory data reset.

To avoid permanent damage to your device, do not interrupt a factory data reset procedure.

1. Back up any important data that is saved on the internal memory of your device to a memory card or other non-internal memory. If you have any encrypted files stored on an SD card, you should also remove the encryption to ensure you can still access them after the reset.
2. Find and tap Settings → System > Reset.
3. Tap Factory data reset → Reset phone.
4. If required, draw your screen unlock pattern or enter your screen unlock password or PIN to continue.
5. To confirm, tap Erase everything.

Your device does not revert to an earlier software version of Android when you perform a factory data reset.

Before performing a software repair, make sure you know your Google account username and password. Depending on your security settings, you may need to enter them in order to restart the device after a software repair.

1. Make sure that Xperia Companion is installed on your PC or Mac.
2. Open the Xperia Companion software on the computer and click Software repair on the main screen.
3. Follow the on-screen instructions to reinstall the software and complete the repair.