It was a software update to VS98624C. I never had any problems turning the phone on before, but a couple hours after the update I discovered that I could not turn the phone on using the power button. Also, although the phone would ring, the screen would not come on and there was no way to answer an incoming call. Similarly, the alarm clock would go off but again the screen would not come on and you could not turn the alarm off. The only way to turn it on was to plug it into a power source. Once I got it working again, it would usually turn on if I used the phone within a half hour of the last use, although occasionally it wouldn't. If I hadn't used the phone in more than an hour, it usually would not turn back on and I would have to plug it back in to reactivate it. The screen protector that came with the phone covered the proximity sensor. Since I have taken that off, I have not had any problems getting the phone to turn on.
You will see on a different thread that someone called woodhenge studios says he used some app to recalibrate his proximity sensor in order to fix his problem. I'm not sure I would want to try that solution, but my taking off the screen protector and replacing it with an old LG g2 screen protector seems to have gotten the phone working again. The old screen protector is smaller, and does not cover the proximity sensor
