You currently can’t complete gem store purchases using PayPal. At the point where you click “Proceed to PayPal” it used to open a purchase window on PayPal.com where you could complete your transaction. Now it does not launch the browser at all, and if you have a browser open it does not link to PayPal and the purchase, thus you can’t complete the transaction. After a few moments an in game window opens, saying transaction complete. Of course since you could not complete the transaction at PayPal, no gems or money changed hands.