If you have a valid license key but lost the installer, you can still retrieve it through official Claris channels:
FileMaker Pro Advanced 16 is no longer available as a free download from official sources because it reached its on September 18, 2020 . While you cannot download it legally for free, here is how you can access the installer if you already own a license or are looking for modern alternatives. Official Ways to Access Version 16 FileMaker Pro Advanced 16 for Mac Free Download
Since version 16 is outdated and may not run on recent macOS versions, Claris offers newer ways to use the software: If you have a valid license key but
: While full installers are restricted, you can still download the 16.0.5 software update from the official Claris knowledge base. Modern Free Alternatives Modern Free Alternatives