On the Original Prusa XL, communication with the peripheral boards (e.g. Dwarf board) is achieved using the MODBUS protocol. In MODBUS, there are two types of devices: the master and the slave, also known, respectively, as client and server. On Original Prusa XL firmware, the master is the XLBuddy, and each slave is called puppy.
After assigning an address to each puppy, the XLBuddy establishes communication with a specific puppy by sending a request. If the puppy does not respond to the request, the printer will show the message: "Puppy # not responding".
Error name: Puppy not responding
Error code: #17514
The error message will specify the name of the puppy that is not responding.
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.
Inspect the wiring between the Sandwich board and the indicated puppy for a cable positioned into an incorrect port, a loose connection, or a visibly broken cable.