Hello Shembo,
I have had the same issue over the past couple of weeks. I recently emailed WGT administrators to resolve this issue. They were quick to respond and were very helpful. The items they requested were;
Individuals screen name you wish to invite,
Date you sent original invite,
and Name of your country club.
I had the members that I had invited in the club within 48 hours after contacting WGT. The link to contact them is on the lower right corner of this page.