Why can't my friends do anything in Minecraft Agrarian Skies?

This question is more for Minecraft Modpack specialists so they don't know how to scroll right away!

I just wanted to test the Minecraft Modpack Agrarian Skies from Twitch in multiplayer with my friends and when my friends were on the server they couldn't open, dismantle or place anything.

Maybe one of you knows how to fix this error.

PS: The Modpack plays on version 1.6.4

There's a spawn protection on Minecraft servers, but this only applies within a radius of 16 blocks around the world spawn. You can display these in the server.properties.

It may be that you have to give them surgery, it was exactly the same with a friend's server (I couldn't do anything).