Have you tried this?
There are a few things you should try first when you experience problems with your device:
- Press and hold down the power key. In the menu that opens, tap Restart. The device should restart automatically.
- If the restart procedure described above does not work, detach the cover of the memory card slot. Then, using the tip of a pen or a similar object, press and hold down the OFF button. Wait for your device to turn off automatically, then restart it.
- Update your device to ensure that you have optimal performance and the latest enhancements. Read more about how to update and find latest software version.
- Reset your device to its original settings. Under Settings, tap Backup & reset > Factory data reset > Reset tablet > Erase everything. Don't forget to back up any important data saved on the internal memory of your device.
If you enabled the security feature, Protection by my Xperia, on your device, you are asked to input the Google™ account credentials you used to activate Protection by my Xperia after you perform a factory data reset.
- If you can’t access the Settings menu on your device, connect it to a computer and use the Xperia™ Companion software to reset your device. Open Xperia™ Companion on your computer and click Software repair. Follow the instructions that appear on the screen. Don't forget to back up any important data saved on the internal memory of your device. For more information and installation instructions, go to the Xperia™ Companion web page for Windows or Mac OS.