Because CS5.5 is older, you will likely encounter issues. Here are fixes for the top five problems:
Adobe’s CS5.5 activation servers are still active but finicky. Try: After effects cs5.5 1 link
Many torrent sites and file hosts claim to offer "After Effects CS5.5 1 link". Examples include: Because CS5
Intel Core 2 Duo or AMD Phenom II (64-bit support required). OS: Windows 7 or Mac OS X v10.5.8. RAM: 3GB minimum (4GB or more recommended). Examples include: Intel Core 2 Duo or AMD
A is a convenience term from the era of split archives, but today it’s often a vector for malware. Only download if you can verify the source’s trustworthiness and you possess a valid license. For most users, moving to DaVinci Resolve (free) or subscribing to After Effects CC is safer and more practical.