This version is widely known for being the first to support macOS High Sierra (10.13.2).
For the license code, explain the trial versus full license. If they have a purchase date before a certain time, they might be eligible for the version 12 license. Otherwise, newer versions might require different activation keys.
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Official Source: The most secure way to download Pro Tools 12.8.3 is through your Avid Master Account under the "My Products" or "Download Center" tabs.
Avid Link: Use the Avid Link application to manage downloads directly on your Mac. System Requirements & Compatibility
Ideal for more casual creators who are curious about the Pro Tools workflow. Pro Tools Intro is free forever.