Adobe Photoshop CS6 licencing fail at login window stage

Old Creative Suite installers are not compatible with Sierra, High Sierra or Mojave without terminal workarounds.

https://helpx.adobe.com/creative-cloud/kb/install-creative-suite-mac-os-sierra.html

CS5 and CS6 are on life support. But they can still be activated providing you have the following:
1. your original media (disks or downloads) you received at purchase and a way to read them,
2. a legitimate serial number for that version, language and platform (Win/Mac) and if it was an upgrade, a qualifying serial number from an older product,
3. an older operating system that can support legacy 32-bit apps.

Legacy Creative Suite is discontinued & unsupported. Use at your own risk.

Supported versions of Photoshop:
- https://helpx.adobe.com/photoshop/kb/supported-versions.html

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https://tinyurl.com/10791730

1 - CS6 is from 2012 and is no longer supported

2 - Based on past messages (I am on Windows, so this is not from direct experience) When you are installing or updating on a Mac, that is your Mac asking you to prove that you have permission by asking for your COMPUTER password, not your Adobe password