Am using audio macros but no audio will play? (Sugarcube 2)

I am attempting to make a looping background music track that won't restart every passage. I am using these macros in my StoryInit passage:

<<cacheaudio "bgm" "Audio/temple_of_the_mystics.wav">>
<<audio "bgm" loop play>>

My audio is saved in the twine stories folder, in a subfolder called "Audio" as above

Is it just because a .wav is too big to load? I'm trying to get the structure in more than anything.

Any advice would be much appreciated! I'm sure I'm missing something obvious.