My friends cant join me even though the world is multiplayer and sometimes i try inviting them and they dont get the invite

My friends cant join me when my world is multiplayer and i changed my settings on xbox and in the game of who can join but they cant join for some reason. When they are playing i can join their world. Sometimes when they wanna play with me i invite them and then sometimes they dont get the invites. I try inviting them like 7 times and they would still not get the notification. Please help fix this bug