Solution for you!
Perform the following procedure to upgrade the firmware:
1. Remove the additionally installed tray from the printer
2. Then perform an upgrade
3. After you have sent the file to the printer, you have to wait at least 30 minutes until the update
is completed. (The maximum time experienced was nearly 45 minuteƐ)
The printer will display if the RFU is finished
4. After that, you have to power off the printer manually and restart the printer but without trays
5. After the printer reboots, you will see READY displayed
6. Power off the printer again, and add paper trays and power on again