Do you have another option when you see that Buy Now button? I see the same screen, but there's another button that says register, or license or something like that. I cannot get it to come up right now, of course. But, it's to the left of the buy now button and when I click on that, it logs me into the Cloud and lets Photoshop open.
Yes I have a cloud subscription and am logging in with that account. When I log in it appears to recognize me. In fact when I launch CS6 it says I have a ton of days on my "trial." I click to activate or register, enter my adobe account info which makes it happy. I am fine for a day or so and then when I restart CS6 (I am having to do so often due to some incompatibilities with running third party scripts in CS5 while CS6 is open) it makes me register the software again. Actually I have had to do it in other programs as well. AI6, and Acrobat.
What type of system optimization utilities are you using? Do you regularly run some type of registry cleaner? Have you tried logging in under a newly created administrator account?
The fact that the behavior only happens every day would seem to indicate that something is modifying the product registration information regularly on your computer.
North America
Europe, Middle East and Africa
Asia Pacific