Compare this to the latest known version (see Part 5 below). If you have, for example, version 10.1.0 or higher, you are likely up to date.
Denon AVR-591 Firmware Deep Dive: The Elusive Update & Why You Probably Don’t Need It denon avr-591 firmware update
A factory reset is often the most effective "update" for legacy units, as it clears corrupt settings and initializes the microprocessor. Method 1 (Rear Panel): Compare this to the latest known version (see Part 5 below)
The Denon AVR-591 is a legacy device. A firmware update may breathe another 2–3 years of reliable life into it, but it will never support 4K HDR, Dolby Atmos, or HDMI 2.1. Use the USB method, follow the instructions exactly, and you’ll likely see improvements in stability. Method 1 (Rear Panel): The Denon AVR-591 is
A: Unplug the receiver – it’s frozen. Restart from Part 6 recovery. Try a different USB (2GB, not USB 3.0).