: You cannot update this receiver through an on-screen "Check for Update" menu as you would with modern Denon AVRs .
Many users report that the network update server for the AVR-591 is offline. Try this only if USB fails. denon avr-591 firmware update
Before attempting an update, verify your current version to see if one is actually needed. How to update my Denon AVR : You cannot update this receiver through an