Neptune 4 printers - error message "Option serial in section mcu must be specified"

Issue Details

Your Neptune printer displays the following error message: "Option serial in section mcu must be specified.. Once the underlying issue is corrected, use the RESTART . command to reload the config and restart the host.. Printer is halted."

Why it happened

The motherboard firmware is missing a configuration file needed to start normally.

How to fix it

Visit the link below for your printer model & download its specific firmware

• Neptune 4 and Neptune 4 Pro
• Neptune 4 Plus and Neptune 4 Max

Extract the zip file, copy the folder ELEGOO_UPDATE_DIR, paste it to a USB stick and plug it to the printer

1. On the error screen, press the white exit arrow on the top-right

   

2. Press the light-blue up-arrow at the bottom

   

3. Press Confirm, wait for the update to complete and restart the printer
4. Go to Settings, press Factory Reset and wait for it to restart
5. Go to Level, set your Z-offset and do Automatic Levelling
6. Press the floppy disk icon on the top-right to save

Note: If your printer has a Type-C print-head-cable, and will not upload the firmware from the USB stick, you will need to follow the Option 2 steps on the links above to flash the EMMC board with a recovery image.