So I figured out how to solve this problem. I also couldn't accept the clan invites via the elite website as it always sent me to the connect page.
Tell the clan leader to invite you via the Xbox 360/ PS3 Elite App, then accept that invitation using the Xbox 360/ PS3 Elite App.
The invite via the Xbox 360/ PS3 Elite App is important as there have been cases of invites not showing on the Xbox 360/ PS3 Elite App when sent from a PC.
Another buddy of mine said also said that accepting the invite on an Iphone/ Android App would work. However I have not tested this.
Hope this helps!
On another note I would like to appeal to every rational humanbeing to NOT resubscribe to Elite Premium. Activision released a unfinshed, some may say broken product and their customer support does not seem to care about our concerns. A company should care about their customers. We should not/cannot support this!
Have a nice day!