Trouble inviting friends or receiving invites on Yatzy Addict game on my Ipad?

I have played a Yatzy and invited friends/received invites for years with no problem. All of a sudden I cannot do either. When a friend has tried to invite me it comes up as 'failed', and when I try to invite, the 'circle' just keeps going around for so long I am just forced to cancel. Then I can no longer play the game/or am accepted into Game Center, and have to log completely out before starting all over again. I have tried logging on/off (as mentioned), logging in and out of Game Center and also closing off my Yatzy app and reopening, all to no avail. Am at a complete loss. Any help would be great!