I am not fully convinced that it would not work because of pro restrictions. Even though I havent used the plugin and a large file upload for ionic view. It works for me using json files and images in assets, so why not audio files?
Have you used git add tonexplicitly include the asset folder?
Add a github repo to see if everything is pushed at all
Use git status to see which files are being tracked/changed (or some other git command)
Does it still work on android using ionic cordova run android?
Are u using ionic view on android or ios? It could be you are making a wrong referral to the file location? Show the code whichh says how you refer