I tried doing Firmware Update with Controller and GO hooked the OTG Cable to Controller than Micro Cable to it and to Craft. But it would not connect to craft, tried restarting one and or the other than bot but could not connect.
So I unhooked from Controller and used PC with Assistant and Upgraded Fine.
I than Upgraded each Battery Firmware through Controller fine as well.
Why would it not make connection the first time with controller should OTG be Plugged in Craft or Controller maybe?
Not sure why it didn't work. My brother downloaded the update onto his go app and then connected to craft and updated that. After the update was done he changed battery to update each one of them too. I will do mine later the same way.
Me either and have done many a firmware on many different type electronics so it is not like I'm a newbie type, seems like It could be the actual Plug on Controller or the Littile OTG Plug ruled out the Longer one as I used that to test it to upgrade on pc
When upgrading the remote, please connect your mobile device to the remote with USB cable, make sure the internet is fine and power is enough, then run APP, you could upgrade it.
While for the aircraft, you could upgrade it through Assistant 2 as you have done, or you could connect OTG cable to your aircraft, then connect your mobile device to the OTG cable with another cable, run APP, you could upgrade aircraft.
Hope this tutorial helps: