Assuming you selected something other than default MOH in the drop down, double check what is in the dial plan for your IVR.
Dial Plan>Dial Plan Manager> find dial plan for IVR in question. Usually close to order 100.
Click to view dial plan then click the XML box in top right.
Check the line with "transfer_ringback=..." to verify it shows correct music source.
If correct, flush your cache. If it is incorrect, it could be a bug that needs to be reported.