Now that you've deleted the device from the app and your iPhone's settings, you will need to pair your GoPro as a new device. Please follow these instructions:
Open the GoPro App and select "Connect Your Camera".
Press the "Add New" button.
Select your camera model
On the front of the camera, press the mode button until you see "Setup"
Press the shutter button to select into the "Setup" Menu
Press the shutter button to select Wi-Fi
Press the mode button to scroll down to "GoPro App" then press the shutter button
Press the "Continue" button in the app
Select your camera from the list (e.g. GoPro 1411....)
Select "Pair My Camera"
Enter the PIN number that is listed on the camera's LCD Screen
Connect to the cameras Wi-Fi network