If your receiver gets stuck in a "firmware loop" (a common issue reported by users during updates), you can perform a : Turn off the unit.
Firmware is the operating system of your receiver. It controls how the hardware interprets video signals, how the network card communicates with streaming services, and how the remote control interacts with the user interface. Denon Avr X4000 Firmware Update
If your receiver is in a location where Ethernet is unavailable, or if the network card is glitching preventing the download, you can update via a USB flash drive. This is often the recommended method for "clean" installs. If your receiver gets stuck in a "firmware