FBM Auto-Authorized Open Return for 31 days yet no package has been shipped?

Hey,

I have a customer who requested a refund 31 days ago, and it got auto-authorized by Amazon. However, there has been no activity on the USPS return tracking # since the request was approved. Given that the 30 day window has closed and he has yet to ship the package, how can I cancel the return and get my money back from Amazon, assuming it’s already been taken out of my account?