Hi there 
Hmm, I’m uncertain why the audio buffer is failing to load in the browser from inside of Foundry specifically when it previously was, but .mp3 files are notorious for having streaming issues.
One thing you could try is to use the optional Forge More Awesomeness module which helps resolve some issues when streaming audio from CDN.
If that doesn’t resolve it, another recommendation would be to change the format over to .ogg, which works much better for streaming in my personal experience 
Hope that helps!