Can't extend my license

Hi. I got an email saying that my UsersWP license will expire soon and that I need to renew it. The email provides a link to click on to do so. When I click on the link, I come to a Checkout page that simply says, “Your cart is empty,” with nothing else. I then went to my Purchase History on my profile page and saw an entry for the license. When I click on the “View Licenses” link, it takes me to a page that shows the current license as active, with an expiration date of July 14, 2018. There is also a link, “Extend license,” and when I click that (thinking that it will extend my license for another year), I get back to the Checkout page that simply says, “Your cart is empty.” Can you please help me extend my license? Thanks!