Worlds has been offline for almost half a year now, if you still want to chat with other users then there is now an alternative server you can connect to.

Add "WorldServer=worldserver://test.libreworlds.org:32147" to [Runtime] in your override.ini (you should have this if you've ever installed a custom skin, create it if you don't)

Support is provided over Discord: https://discord.gg/xfeddMzVQA

Viewing avatars requires you set up an upgrade server, I won't talk about that in this OP

Where do I find the runtime and override.ini?

Wherever you installed Worlds.