SOLUTION
I had the same issue connecting my gopro hero 8 Black with my one plus 6 for moths untill I saw a solution on a gopro forum.
To connect successfully to your gopro you have to manually connect it trough your phone's wifi setting.
Look for your gopro name and use the password from you gopro. You can find this password in the connection setting under the "camera info" (at least it is for my gopro hero 8 black)
It's a little annoying that this has to be done repeatedly as the error popup returns every time I reuse the app, but I can at least view all my gopro media trough my phone again.
Last edited: Oct 16, 2020