remote controller firmware update

Hello! I upgraded my GL300C controller using DJI GO app to the latest firmware. After the upgrade, it doesn't power on. I found a recovery mode combination (C1+Shutter button), but when I try to upgrade in this mode, the controller starts beeping for few seconds, and after that, the lights go...

I wonder if anyone on this forum has come across the following issue I am having with my Phantom 3 Pro. The aircraft has had a successful firmware update to the latest (as at 29th August 2016), as have all three batteries I have. I believe, in fact I'm sure that the remote controller has also...