L4D2 on 360 always getting the "Failed to join games"

[Severance]

JaggedSac said:

NAT could be an issue depending on the size of the userbase.  Regardless of NAT being the issue, userbase is probably the main culprit.  Is this a recent development for you?

i'm trying it right now, like i said i've only played it once when i first got the game, but only once.