Cant add new ramification on multi variant

[Kaladin]

Hi guys,

Got a problem here, I've tested on multiple browsers (Chrome, Mozilla and IE) and none of them work, I didn't have this problem before however my client has made me aware of it after trying to add a new product a few months after I have finished the site.
When I try to add a new ramification to the multi variant, in this case, I wish to add Paper type after I add Frame Size, but the "new" button or green+ icon next to it do nothing.
http://imgur.com/RxDztTb

Here is a picture of exactly where and what I am talking about.
Any solution or ideas please?

Thanks a lot.