World Composition and level streaming hosted multiplayer clients falling through map

You need to place that plane outside the player, where normaly the player spawn spot, on the terrain. this is a rapid fix and it’s work for me.

the other solution for this is to desactivate the gravity of your character or set it to 0 , than create a linetrace and detect if it’s collide with worldstatic. If so you re-enable the gravity.