These are links that start with sop:// instead of http:// ?

Do the links work in Edge?

What program on your system is supposed to play the link, or what plugin do you remember using for them? If you did a Windows 8 => Windows 10 upgrade, it's possible that needs to be reinstalled. If this is a new system, it almost certainly would need to be installed.

Links start with sop:// and they are supposed to open Sopcast, which is in installed on my PC!

This is the way things were working on Windows 8 . I was just accesing a sop:// link and the Sopcast software was starting and buffering the channel.

I didn't make an update from Windows 8. I have installed separately my Windows 10.

Can you try the sop:// link in Edge? Maybe the protocol-to-program association wasn't created automatically when you installed sopcast and Edge can help create it.

When I am using Microsoft Edge it brings up a window with : "You'll need a new app to open this sop." with just one option: Look for an app in the Store. I have tried to reinstall sopcast, but the same thing is happening. :(

Can you find a Sopcast support/discussion site where other Windows 10 users have described how to get the program registered at the system level to handle the sop:// protocol? I didn't find anything quickly in a Google search, but some forums don't index very well, so it could be out there.

I did make a fabulous research on Google but I didn't find anything, this is why I came here. Mozila support was my last hope...

Okay, hopefully someone else can figure it out. I don't get my hands on Windows 10 very often. (And it's on a slow system that doesn't really need any new software installed on it...)