I fixed this on Mac M2 chip running Monterrey. The issue is Mac is unable to load .ogg audio files (which is why it runs fine at first, when it only has to load .wav files). If you’re fine playing without audio, just delete all the .ogg files. If not, read below…
Go to /Users/~/pkmn_insurg , drive C, Program Files x86, Pokemon Insurgence, Audio. Then use an audio converter to convert all the .ogg files in the BGM and SE folders into .wav files. I used “MediaHuman audio converter”, it was free. Delete all the .ogg files from those folders and replace them with the newly converted .wav files. Then, as a final step, you have to manually change all the file name extensions of the converted files from .wav to .ogg
Hope I help someone.