From the SketchUp website in both FF and Chrome, when clicking on Subscribe for any plan a loading sequence appears and the page never loads. Must be costing your company lots of money, this has been happening over the last week.
the link of SketchUp Shop does work here (w/ latest Fx):
https://ecom-prd.trimblepaas.com/cart/#/buy?sku=SKP-SHOP-YR-WEB-01