servers not working

[applecore-productions]

every time I try to connect to servers besides what's on the list they don't work

[ChristopherHX]

Cannot reproduce. The client and the server version must match, sometimes are a small number of Minecraft Versions compatible with each other.

You should know, this launcher won't have new version support as fast as the official Stores so this can cause your problem.
You can play multiplayer if all members use the same ( old ) version, everything else is not supported by the game.
It is still possible to use multiplayer with Minecraft 1.12.0, if you don't mix Minecraft Versions.