There is another way to get your RC updated with a USB pen-drive.
I have placed a RC reset file on one of my websites, this will restore your RC to factory condition.
The instructions are:
1. First download this RC reset patch file by putting it on a pen-drive and update the RC with it.
http://www.weymouth-angling.co.uk/gs_ofdm.bin
2. Then turn off the RC, reconnect the ipad/android and delete the existing DJI Go App, then download it again and re-install it.
3. Restart the RC and then start the newly installed DJI GO App.
4. Click the "Upgrade Required" message and in the next section the App will offer to download the latest FW file and install it, click "download FW file" and when it has downloaded, install it.