Many radio stations are moving to use https (instead of http) to deliver their audio streams.
This is not supported by many Squeezebox devices.
The problem has been hidden for many users because they run LMS (aka SlimServer and other names) on their local LAN and then they access the problem streams by having LMS act as a proxy.
"MySqueezebox.com" does not act as a proxy for streams.

However, there might be a non-https stream available for the particular stations that you want to play ... in which case you can add the stream URL as a Favourite.
Easiest way to do that is via the web interface at https://www.mysqueezebox.com/settings/favorites

If you give the name plus some extra info (e.g. URL to their web site) someone might be able to help you with a stream URL.