I've seen some posts lately about people having this problem... and then I started to experience it myself. I tried using 3 chargers and some different cables and the headset still would not start charging or power on. I thought the unit was dead.
I contacted Oculus Support and it, ultimately, was decided that I would need to return it for service. However, after receiving a mailing label from them and an instruction to "factory reset" the device if I could before shipping I got to thinking, "I can't factory reset it because I can't get it to charge or power on... but maybe I can plug it into my computer and wipe it like a flash drive."
So, I plugged it into a *powered* USB hub on my computer and... the charging light lit up and the oculus symbol popped up in the headset display. The computer did not show that it was connected, but I left it sit that way for a couple hours and then powered it up (while still connected to the computer.) It booted up fine and the computer did see it.
I removed it from the computer, tested it out, and then tried hooking it up to the chargers that it wouldn't work with earlier. It now will charge with them.
It seems like plugging the "dead" unit into my computer (not sure if it needs to be a powered USB hub or not) seemed to trigger some kind of "wake state" that other chargers (including the one that came with it) could not.
I'm not sure if this will help anyone out there with their charge/power-on issue, but this is what worked for me.