I'm experiencing the same on Firefox; if it helps at all I just ran into this issue with a jam game I submitted and went through hell at 1AM trying to figure out the cause. For me it was the music file being too big, it seems it needs to be <~2MB (rough approximation, mine worked at 1.76MB). So maybe double check if you have any assets in that size range?
Hope it helps, your game looks cool and I look forward to trying it!