Okay so earlier today I tried to host a private match on a custom game mode I made for 2 of my friends. Problem is, when I almost get to the lobby, we get a message saying something like;

"You have been invited to a game mode you can only get through the Battle Pack downloadable content. You can upgrade to this content and join in the fun with your friends, or cancel this invite and play on your own... all alone."

Then it tells me that the Battle Pack includes 6 new weapons, 30 more single player missions, a body count game mode and much more. I could press A to upgrade to the content or B to cancel. If I press A it shows me the xbox live marketplace for worms, but there is nothing there other than the premium theme, and if I press B it brings me back to the xbox live menu.

I don't know why this happens because it's my own game mode and I haven't even been invited, I hosted the game. Has anybody had anything similar to this or can help me? I think I would probably buy this content if I could.
Thanks.

likely its an issue with the same message being sent to all three teams though its only one without the addon

I am having the same problem when hosting a match with my own gametype, although, my friend is still able to host a very similar gametype. The DLC in question isn't even available on the marketplace yet.

Team17 accidentally introduced a bug in the latest title update. As a work around, create 2 dummy schemes then have your custom scheme positioned in the list after them, host with your scheme.