What happened?
The printer is showing the message: "Unknown error"
Error name: ESP unknown error
Error code: #17506
On the Original Prusa XL, the XLBuddy board includes a WiFi module, the ESP32. needed to achieve WiFi connectivity. The error is triggered in case the printer detects an undefined problem with the ESP32 board.
How to fix it?
Re-flash firmware
The firmware needed for the ESP32 module is included in the XL firmware file. Download the firmware and if necessary the bootloader, and transfer it to your USB drive. Make sure to unmount the drive from your operating system before physically removing it.
Insert the USB drive back into the printer and reboot the printer using the reset button directly next to the knob to initiate the flashing procedure. In case the procedure does not start, reboot the printer again by pressing the same reset button, and while the printer is booting up, press once the rotating knob.
The printer will let you know when the flashing is done. When installing the bootloader along with the firmware, it may take several minutes.
A visual inspection
Access the XLBuddy board, and locate the ESP32 module. Inspect the ESP32 board for any visible damage.