Hi,
Due to the Autodesk licensing policy for third-party developers, we have licenses only for the latest 3DS Max release, and five versions before.
At this moment, that includes Max 2020 to 2025 (our license of Max 2019 just expired... we must update our documentation).
We can provide compatibility with old Max versions (as 2013), just compiling the plugins with the appropiate Max SDK.
Although we cannot test them or provide support, at least the plugin is available for customers who need it.
But libraries is a different issue. Since they are saved using Max files, we have not way to create them for old versions.
Some RC libraries were created years ago, and are compatible yet. But latest libraries (and the revamped ones) load only with recent Max versions.
We are working to create a custom portable format, and migrate all libraries. That will solve this limitation completely. But it will take some time yet.