If it chugs once, that's "turning over'—i.e. the engine is rotating. Sounds as though the starter isn't getting full power for some reason, which could be a bad battery (even though it's new—it isn't too common, but it does happen sometimes that they have manufacturing defects), a discharged battery, or a bad connection somewhere. Check the battery cables and ground connections. Included in these checks are making sure that the wires themselves are firmly attached to the battery clamps and are not broken or chafed there; I've seen at least one case where the wire looked fine but was actually not attached to the battery clamp internally due to corrosion etc.
Do you have an "emergency start" button that connects in the house battery?