Ensure that or Plugins (specifically Keylight) is selected. Option 2: Manual Installation
Drop a comment below (with your OS and AE version) and I’ll help you find the right file.
Once you have the installer package (usually a .exe for Windows or .pkg / .dmg for Mac), follow these steps:
A: Not legally. Adobe support no longer issues CS5 replacements. You would need to purchase a used CS5 license (eBay/Craigslist) or upgrade to a modern After Effects subscription.