Stumbled upon this post from the LibreSwan team detailing that IPSec is essentially impossible on Amazon's Web Servers (regardless of how they are tweaked or configured).
More concerning though is the fact that general tests to check connectivity provided a false positive
https://libreswan.org/wiki/Interoperability
More concerning though is the fact that general tests to check connectivity provided a false positive
https://libreswan.org/wiki/Interoperability