Share your experience!
Hi, I had a black screen, would not start up again, nor connect with USB to Sony Companion. Only the purple light was still blinking
The fix was very easy: Press on/off button + sound-button for 10 seconds; it came to life again.
Goodluck with fixing your problem
Hi @Bert1984, welcome to our forum and thank you for sharing the solution to the unexpected behaviour that you were experiencing! 
Pressing the power button and volume down button at the same time will force a restart or a shut down, kinda like removing the battery on older devices that had a battery that you could remove.
Have a great day!
Thank u. My device was updating and retarting but went blwnk followed ur advice and it worked.
i tried everything on this list and it is not working
Hi @ryan30, sorry to hear about your device. 
Is the device turned on and the device is turned off, or is the device turned off and can't be powered on?
Since it didn't work to hold the power button and the volume up key for 10 seconds, try holding both of them down for 2 minutes > ignore all vibrations > connect the device to a charger and wait for the charging icon to show up on the screen > try powering on the device.
If there is no change, try performing a software repair using Xperia Companion, but keep in mind that all data stored on the internal storage will be deleted in this progress.
Let me know if that helps!