As Minnreefer said, first check the PayPal page and see if the payment went through.

Usually for me the order shows "paid" within a few minutes of submitting a Paypal payment.

Log out and back in to the HK site and hit "refresh" a few times too, just to clear your cache.

If after doing all of this the order does not show up as "paid" check the items to see that all are in stock, I've also seen out of stock items foul things up a bit, as well as ordering batteries.

Note when ordering batteries I recommend using the USA warehouse whenever possible. Due to new restrictions on shipping LiPo's via air, most LiPo packs are now shipping via Europe... ( yeah it makes no sense... ).

Anyway if after 3 days the order still doesn't show up as paid, it's time to get on "Live chat" and also send an e-mail. It takes 2-3 days to get a response via e-mail.