Some users modify internal configuration files to manually increment the trial serial key.
Move everything inside SLCache and SLStore to the Trash. Do not delete the folders themselves, just the files inside. Clear Local Preferences: Photoshop Cs6 Trial Expired Reset Osx
If you can run Photoshop CS6 in a virtual machine (like VirtualBox with macOS High Sierra), do that. Otherwise, use a modern alternative. Some users modify internal configuration files to manually