I can send invites but no one will get them and same thing with the opposite

Check your NAT settings and if all is correct try removing the account from the console, doing a hard restart, hold the power button for 10 seconds while the system is on, and then re-adding the account

If you are unsure how to check your NAT type here are the steps (You want an Open or Moderate NAT type, if it is Strict it will cause issues with multiplayer.):

1. Open the guide by pressing the Xbox button in the center of your controller.
2. Scroll right in the guide to the System area
3. Select Settings.
4. Select Network.
5. Select Network Settings.
6. Select Test NAT Type.

The only thing i can think of is to keep trying to send the invitation or keep refreshing to get it to send.

Ok, so the Xbox One preview. I know that the participants can send a invite to any of there friends. When a friend invites you, you can register for the preview after a certain verification then you can be invited ( so it is not a guarantee you will get
invited) the Xbox One preview.

So if you have any friends that are participating in the preview you can ask them if they want to invite you.

To Whom it may concern,

I am having issues sending Game Invites, both through the console and through the Game (Game is COD WWII).

Anyhow I have reboot my Xbox, I have reset it back to Factory, still not able to send Game Invites, I can however send a Party Invite.

Even if we are in the same party I still can not send them an invite. (Multiple People not just one).

Any ideas.

Also try and restart the game itself not just the Xbox, I have seen a trend in recent COD games where it does not allow you to send them but if you press the Xbox menu button and then the menu button on the application and Quit the game and reboot it, it often
corrects itself.