Jim, my guess would be that the mechanism for 2.6 upgrades is not in place yet then (when I checked this afternoon) since my only option for MA3, after keying in my 2.6 keycode, is the 9.99 upgrade. So I'll wait a few more days for that to happen.
However, on the SereneScreen report page, you are correct in that that is not what I'm seeing. The box you're showing at the top there... I have the lines in it but not the letters. So I can't enter anything to verify it. Also, it appears at the bottom of my screen, though I think I'm in Customer Support as opposed to Technical Support. (I'm clicking Contact this from the menu running down the left hand side of the screen.)
I looked again and it appears that clicking Support (instead of Contact Us) actually brings you to a different place. Perhaps if I follow the right chain of clicks through that page I'll get to a page where I can properly contact someone but for now, I cannot find it, and do not get a page that looks exactly like yours above.
ETA - Ah hah! Found how you got to your screen. After clicking Support, then click on Support again from within the "Email us" section of that page, and now my screen looks exactly like yours does, with the codes and all. If you instead just click on the Contact Us link from the very top menu, while you're logged into a Prolific account, then you get a slightly different screen where the CAPTCHA box appears at the bottom of the page instead of the top, but it's missing the letters which are supposed to appear in the box.
So I guess I'll go ahead and email them and express my disapproval for not implementing the upgrade process properly, especially when I only bought the program last week.