Help with Marantz NR1604 Firmware

Hello everyone, I have an NR1506 stuck in a firmware loop. The device shows neither the FW version nor the MAC address. I've been searching for a USB firmware for a year now, any version would do. Maybe someone here can help me?
 
According to the manual, the firmware is downloaded automatically by the device.
So the chance that you will find it somewhere is, in my opinion, impossible.
Do you get any of these messages? Is the device connected via LAN or WiFi?

Firmware.jpg