I cannot connect to additional minecraft PE servers

Hello! I am writing about an issue that I have been experiencing on Minecraft Pocket Edition. The issue is, that whenever I attempt to join a additional server it shows no players online and the ping is a red symbol. This happens every time I try. I have tried reconnecting wifi, reinstalling the app, updating my multiplayer settings, checking for errors in the server adress etc. It’s weird because it seems I can join the default servers with ease but when it comes to external/additional it fails. Please help!

:)