Unable to join other multiplayer games

When I try to join a multiplayer game on State of Decay 2 Juggernaut, it says unable to connect game- you must have a populated community to join the game. One friend was able to join but I can not. WHY?

At times im unable to join multiplayer games ie forza ( keeps failing to join/host) and bf4 says im in a server and connected to a game but im sat at the home screen with it not allowing me in.

We can invite each other but unable to join and it usually says unable to join player or in some cases the game crashes for the person who tries to join.

k i will try that but i think we are having slightly seperate issues, when i am at the main forza screen were i can go to career or any of the selections if i go to multiplayer and it will say starting multiplay for about a min and then a little message
comes up saying ; multiplayer is currently unavailable please try again later ; so i can't even see multiplayer lobbys are nothing it kicks me back to the main screen

and i have tryed my other games ( madden, rise, need for speed) and multiplayer works in all those games so its strickly a forza five issue