MOH - What bitrate to use for MP3 file?

Just trying to upload an MP3 file for music on hold. I have tried to upload a standard 320kbps file, but the file does not play. What is the highest bitrate I can use that will be compatible? I have found some things online that discuss this, but the posts are from a few years back. Alternatively, would WAV give me better quality? Thanks

8K Mono PCM if you are using G.711 for most of your Voice - If you are using HD Trunks and Endpoints, and you have HD connectivity to the remote sites, you can scale if for G.722 or whatever HD Codec you are using, but that assumes end-2-end HD connectivity, which is rare.

8K Mono PCM usually sounds great as long as it was down-sampled using a program that doesn’t mangle the source material.

Thanks for the advice. Its just for a personal server, but I’ve got Soundbooth, so I’ll give that a go.