Format not accepted error

Often I will upload a .wav file and get an error that says that format is not accepted....except that format is accepted at Pond5. Why am I getting the error? It happens about 20% of the time, which is too frequently. Ideas?

I think I figured it out. Response from the community was underwhelming, just saying! The Pond5 system doesn't seem to want WAV files that have ever been MP3 files (converted.) If I want to upload WAV files to Pond5, they need to always be downloaded and edited as WAV files. I hope this helps someone else out there. Best wishes, Alana