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.
NOTE 1 : Creative Suite installers won't work on macOS Sierra, High Sierra or Mojave without terminal workarounds. See the help article below.
NOTE 2: Legacy Creative Suite will never run on Catalina or Big Sur. Only the latest Creative Cloud products are compatible.
NOTE 3: Legacy Creative Suite is discontinued & unsupported. Use at your own risk.
Beware of fake Adobe reps who may contact you privately offering to sell you software or take control of your computer. It's a scam, run away! Real Adobe employees will never reach out via Outlook, Yahoo, Gmail or Skype.
3 Easy Ways to Identify Genuine Adobe Staff
Nancy O'Shea, Product User & Community Expert
Alt-Web Design & Publishing ~ Web : Print : Graphics : Media