How can I go about downloading Vassal 3.1.5? The current version of VASSAL isn’t compatible with Combat Commander Pacific/New Guinea.
I’m sure you don’t want 3.1.15, but all the releases are here, and every release from 3.2.17 onward is on GitHub.
The module page for CC:Pacific seems confused about what’s required. The table says “3.1.19 or lower” but the text says “Version 1.3 updated for Vassal 3.2.15”, which suggests to me that it would work with 3.2.17 also.
Have you checked that this module doesn’t run with 3.5.8?