How to change character material once in server?

So i built a dedicated server using this tutorial UE4 How to build a Dedicated Server - PT 1 - YouTube and then i built a team selection menu using this tutorial UMG Team Setup in Unreal Engine 4 - YouTube and i cant figure out how to make them work together i made it so when i play it i go into the third person example and when i enter a trigger box it sends me to another world where i have my menu and when i click any of the buttons it sends me to ip address but in the transition to the server o ip address when i try and change materials it doesent show on the server it shows for a split second on my team menu