Does that only work with a paid nostr.build account?
Discussion
I'm pretty sure mp3 is supported on free tier.
If it doesnt work... can I zap you and pay for a month of nostr.build premium for nostr:nprofile1qqsp3yzapfwkyw4cr2vt4xx9s27474lj2pkxhqyfqh79n826pv3fkzqpzpmhxue69uhkummnw3ezumrpdejqzrthwden5te0dehhxtnvdakqz9rhwden5te0wfjkccte9ejxzmt4wvhxjmcru0tqj?
Audio is supported and always has been. We even have a player https://e.nostr.build