Play Fall through the floor on Play

i have a problem with my game since when i select the " Game "Map then click Play i’ll get my character spawned and then i’m able to walk around ( i’m currently using the ThirdPersonCharacter coming with unreal, without any change on it )
but when i start from the main menu screen and then load the level i’ll get my player spawned but will fall down ( looks that doesn’t have collision… ) what i mssing out? i have to posses it after the map is loaded or i have to do anything else?