Instalation Issues of CS6 after HD crash and repacement of the HD.

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

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.

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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.
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3 Easy Ways to Identify Genuine Adobe Staff
https://tinyurl.com/10791730

You may need to enter the serial number. 

If you need to reset activations:

Go to chat and only ask to have your activations reset:

https://helpx.adobe.com/contact.html?rghtup=autoOpen will automatically open the chat window.
Type "Agent" in the chat box to bypass the chatbot and be connected to a person.

You may also be able to contact Adobe by phone:
https://helpx.adobe.com/contact/phone.html