I have been struggling with this same issue for about a year now. I purchased this device 2014 when it first came out at the hefty price of $500. I did a software update via USB and the PC Companion Software and it corrupted the tablet. Resetting the tablet wouldn't work, so Sony had be send it in for repair. I barely used the tablet since then and always stored it in a rigid tablet case, but when i tried to use it about a year ago, i could not power the device on or off using the power button. I contacted Sony in November 2017 requesting to send it in for repair again and they informed me they were moving their repair facility and to contact them back in February 2018. When i did, they refused to repair it because it was out of warranty and to have it repaired by a third-party service center. I tried several times to get information for any service centers that could repair the Xperia, the service centers i contacted stated that they couldn't repair it because they couldn't get Sony parts. Tonight i tried to google for service centers AGAIN and decided to search for my issue and was brought to this thread. I saw your images and decided to give it a try by pressing firmly on the tablet surface beside the power button ... and wallah! It worked and I was able to power it on and can now use the tablet again. THANK YOU to you and other forum posters that take the time to post solutions to help others.
