I have the same issues sometimes on the latest firmware. My problem seems to pop up when I have nut used the drone for some weeks and the battery was still in the drone. Try other batteries and leave then out the drone for some time. Works for me.
If you turn the drone off does is also keep the battery leds in some type of locked state? It does with me when the problema occur
the same cable works on my other phantom 3 pro . I have tried change the batteries accross from the other drohn e who works , but still no live view. Seems the issue is with the lightbrige ?
All these posts about the 15 00 and 08 00 errors always draw a blank, surely someone somewhere has just replaced the board or does an exchange camera/gimbal assembly?