If your Mac is running Mojave or newer, stop here. You need Pro Tools 2019 or later. For Sierra, you are golden.
To download Pro Tools 12.8.3 on your Mac: Pro Tools 12.8 3 Mac Download
Pro Tools 12.8.3, released in December 2017, is widely considered a significant and stable "legacy" version for Mac users, particularly those maintaining older hardware and operating systems. If your Mac is running Mojave or newer, stop here
You would need Pro Tools 2019.6 or newer. released in December 2017