I currently have Photoshop CS2 and purchased and installed an upgrade for it back in 2006. It has not been upgraded since and now today when I tried to access it I get a message saying I have to reactivate it but it won't allow me to do that. How can I upgrade my version of Photoshop?
CS2 is totally outside the upgrade loop. It doesn't qualify for anything.
However, you can still install CS2. You just have to download a special CS2 version, expressly meant for CS2 owners, which requires no activation and also the new key number for that special edition; your old serial number will not work, the new one only works for the new, modified CS2 version.
Adobe decommissioned the old CS2 activation servers, then generated this workaround for CS2 licensees.