Difference between HtmlViewer and Browser

Well, there’s still one stream that I’m having trouble with: Arctic Outpost Radio, https://www.aor.am/
I updated the stream URL from the official site to https://radio.streemlion.com:3715/stream
but it still fails to load in my app, giving this error:

[Error] Failed to load resource: An SSL error has occurred and a secure connection to the server cannot be made. (stream, line 0)

which doesn’t give me much to work with. However, when I paste the stream URL into Firefox, the console also shows an initial error:

But then it appears to reload, and the stream starts and runs. I’m pretty much hopeless at debugging this kind of stuff, so I don’t know what this is telling me.