I have the generic camera installed on my home assistant. It displays the cameras fine in the app on my phone. When i view on a browser it shows me previews of the camera but when i click to view it says Error with media stream contents.
Please see screenshot - Pasteboard - Uploaded Image
Probably there is a problem with the stream settings or url for your camera.
It can be confusing, but the still and stream views of a generic camera are completely separate.
When you look at the first card, you are viewing the still. When you click on it, you are viewing the stream. That might be the first point that you can detect an error with the stream side.
It could also be that your desktop browser doesn’t have suitable codecs for displaying the stream.
I recommend trying to get the stream to play in VLC on your desktop to rule out a problem with the camera or stream itself.