Downloading and activating Photoshop CS (Version 8.0) is no longer officially supported by Adobe. The program is over 20 years old, and its activation servers were permanently shut down years ago. JustAnswer
Even if you have a physical disc or a valid original serial number, they will generally not work because they cannot "call home" to verify the license. Why You Can't Activate Photoshop CS 8 Photoshop CS version 8.0 - Adobe Community download photoshop cs 8 with serial number