Hello,
I have checked all your orders. I only found your original JoomSEF 3 license and its prolongation. I did not find any upgrade from JoomSEF 3 to JoomSEF 4.
So to upgrade to JoomSEF 4, you need to get upgrade product:
www.artio.net/e-shop/joomsef/joomsef-4-upgrade
Note that your free upgrade period you have extended for JoomSEF 3 will be preserved!
When you complete the purchase, only go to Online upgrade in JoomSEF and click "Migrate free to paid". Make sure you have the proper Download ID entered in Configuration / Registration tab.