Neptune 4 Plus and 4 Max eliminate the limit switch sensor and instead use the torque generated by the impact when the belt and motor return to position to determine the zero point.
It is recommended to loosen the belt slightly.If there is no improvement after loosening the belt, please update the firmware to the version in the link below.
https://www.elegoo.com/pages/download
PS: The motherboard firmware and touchscreen firmware are matched and both need to be updated. A mismatch in firmware may cause the printer to function abnormally.
(Turn counterclockwise to loosen, turn clockwise to tighten)