Hi,
I think we've found the problem.
It was in EL_Helpers.dlo. When we released version 2.0, we needed to create EL_Helpers compatible with both versions 2.0 and 1.9.9. This coincided with the release of 1.9.9 SP10. That's why SP9 still works in 3dsMax 2015, but newer versions don't.
Today we patched this version of EL_Helpers.dlo for 3dsMax 2015, and you can download it from this link: EL_Helpers.dlo
You can now install version 1.9.9 SP12, then replace the EL_Helpers.dlo file in the installation folder, typically C:\Program Files\Exlevel\GrowFX_3dsMax_2015\
After that, please let me know the results.
Thanks!