Gopro Video settings are 1080-30 fps or 720-60fps. Edge Hdmi is limited at 1080-30fps (Rpi limitation).
Set your QGC at the same settings (1080-30 or 720-60).
At startup,
1 Start Emlid Edge,
2 Start your GCS and establish wifi connection.
3 Start your Gopro
4 Start Streaming, there is some delays before video appear, no need to maintain start stream button active.
When OK, you can start recording on the camera (or not). You can also record video stream on the computer.
You can check Gopro video out by connecting it to TV Hdmi In or Computer monitor Hdmi In. If fine, it should work with Edge.