4K Production Switcher / GoPro

Newbie with both products (and this forum), sorry.
Atem switcher set up and recognised on control laptop.
Program Output from the switcher on HDMI via a Magewell capture card into a USB port on broadcast laptop.
GoPro is Hero7 Black outputting via HDMI to Cam 1 input on switcher. Set to 1080p/50fps. Switcher also set to 1080p/50fps
Camera 1 selected via switcher front panel and in control software.
No video signal gets through.

When I plug the HDMI cable from the GoPro into a TV, the TV picks up and displays the GoPro signal.
When I plug the same cable into the switcher there is no video on the screen of the switcher or transmitted to the receiving laptop.
If I connect the multi-output or program output from switcher to TV or broadcast laptop, it plainly recognises the input capture device and even displays audio signal from the GoPro in the VU meter, but video is black/blank.
Probably a "settings" issue. Any guidance?

There was some advice for getting a GoPro 7 working with an ATEM in this thread: viewtopic.php?f=4&t=73020#p513812

In general, it can often be helpful to use a video standards converter such as a Blackmagic UpDownCross HD or Decimator MD-HX with a GoPro as it will often output a different resolution over its HDMI output than the camera is set to record to internally.

Thanks, Dave. I'll look at the earlier thread.
I have now read the GoPro manual (if all else fails, right?) from cover to cover and there is absolutely no mention of the HDMI output being at any different resolution/frame rate to what I select in settings.
How deficient is that?

This looks like a quiet backwater of what may once have been some lively topics.
Now that I know where to look, I have been doing some testing.
The GoPro Hero 7 Black, which I am using has (perhaps had, since the Hero 8 has since been released) the highest resolution of the Hero 7’s, capable of 4k @60fps, 2.7k @120fps and 1080p@240fps.
It has two basic settings for eliminating mains frequency flicker depending if you are in a 50Hz environment (like UK) or 60Hz (like USA).
Having set this parameter, the 60Hz (USA) frame rates are basically 30, 60, 120, 240 while the 50Hz (UK) rates are 25, 50, 100, 200.
However, whatever the resolution/shutter speed combination selected for recording onto SD card, the signal is downgraded for output over HDMI and is emitted at 1080p29.97 for all 60Hz settings and 1080p25 for all 50Hz settings.
So the Atem will always display an output if matched to those settings, without the need for any additional hardware.
Also, additional hardware (Decimators or BMD's own equivalent etc) may help match cameras to each other so the Atem will show and switch them all in spite of this, but no amount of hardware will ever recover or improve the signal to a better resolution or frame rate than is output by the camera (over HDMI). In fact, it's a case of the Lowest Common Denominator.