Unable to Complete Upgrade Purchase, Am I Going Mad?

Hi all, I just got the email announcing KM10, so I've updated to it from v9.2 and am in the process of purchasing the upgrade. However, after entering my details and clicking continue, I'm being returned to the purchase page and told I need to accept the terms and conditions before I can proceed. But I don't see any terms and conditions on the page! I'm using Vivaldi 4.3 and have had no problem with other purchases using Fastspring, so I'm not sure where the problem is. Can anyone advise?

Update: I've used Safari instead to purchase the upgrade, and the terms & condition checkbox appeared there. Very odd, I've no idea what would cause that to disappear in Vivaldi! Anyway, purchase has gone through, but something to check with Fastspring perhaps?

I used Vivaldi 4.3.2439.44 (Stable channel) (x86_64) to complete the upgrade transaction without any problem. Maybe it's related to some of the extensions that you are using?

Possibly, although I didn't have many extensions installed to start with. Anyway, panic over for now, and my Vivaldi installation is quite a bit lighter.