I feel his pain.
For some reason, today, I had some real issues switching my JXD S192 on, it would say battery flat, then it would say battery full, but could I hell get it to come on.
Now, I have managed to get it to switch on, and I cannot turn wifi on. I flick the onscreen switch and nothing happens. I have also tried to restore the firmware back to stock, and also use Lord Davons Firmware, but nothing seems to work.
With no WiFi, the device is pretty much dead as a dodo.