The double tap to wakeup feature is not working on my at&t Lumia 920 since yesterday (6/27). I am not sure if any app update got installed that broke it. I don't see anything suspicious in my app download history. I am running 8.1 Developer's Preview. I went to "Touch" setting and toggled the setting multiple times. Also, rebooted and soft reset the device few times, but it didn't resolve the issue. Is anyone else experiencing the same issue?