Adobe Photoshop CS6 Extended was the final version of Photoshop available as a perpetual license before Adobe transitioned to the Creative Cloud (CC) subscription model. If your trial version has expired, or you are facing a "trial expired" message on a previously licensed copy, here is the verified information on how to handle serial numbers and activation today.
: Check the email associated with your original purchase for an order confirmation from Adobe that includes the 24-digit key. Original Packaging The Reality of Photoshop CS6 Serial Numbers Today
The Evolution of Digital Ownership: Navigating Software Life Cycles and Licensing Models Adobe discontinued CS6 in 2013 and no longer
This is tedious and works inconsistently. Most users report the trial still detects a prior expiration. Legal Alternatives (No Activation Required)
via third-party websites is generally not possible through legitimate means. Adobe discontinued CS6 in 2013 and no longer sells new licenses or provides free serial numbers for it. How to Retrieve a Legitimate Serial Number
Troubleshooting Adobe Photoshop CS6 Extended Trial Expiration