Xmax 3 not connecting to klipper

You may have a look between line 268830 to 270569 in your klippy.log. Your config disappeared. That’s why you get “Config error” … “Error: Option ‘serial’ in section ‘mcu’ must be specified”.
Please check your printer.cfg.

Also your Klipper version is dirty.
Git version: ‘v0.10.0-530-g3387a9c2-dirty’
and your Moonraker version also.
webhooks client 281473117064440: {‘program’: ‘Moonraker’, ‘version’: ‘v0.7.1-609-gbdd0222-dirty’}

You could read https://klipper.discourse.group/t/how-to-trouble-shoot point 5.

Good luck, hcet14