Also try this.
Open the WiFi settings on your phone and click on the "advanced" tab. See if there's an option labeled "Manage Networks". If so, click on it. In there you'll see a list of stored network connections, make sure you delete any references to your GoPro camera in there.
Basically android stores all your old connection info in case you need to quickly reconnect later on. However if you change your password in the app, Android ignores this and tries to use the old stored password and this is why you sometimes see a "passkey incorrect" message when trying to reset your WiFi password. So deleting the info from there should help.
Once you do this, you'll need to set up your connection to your camera again as if it's the very first time you've connected to your GoPro.
