The activation servers for CS3 have been retired.
You have to uninstall all CS3 programs and download non-activation versions.
Follow the instructions carefully.
Well, that didn't do much. It's exactly the same as before. After installation, opening an app, exactly the same error message about activation failure. And, I can't find any place else to fill in the new serial key, only options are from the menu; registration and activation. And yes, I did follow the instructions carefully.
Obviously, there's something wrong here. But what? What to do then?
Did you ever get an answer to this??
I got it working. My problem was that the old activation info was still on the computer even after the old program was uninstalled.
After uninstalling, delete the AdobePCD folder from Program Files(x86)\Common Files\Adobe and then re-install the new version which no longer requires activation. It worked for me.