An electric dryer in a US home runs on two 120-volt legs that together supply 240 volts to the heater, while the motor and controls run on one leg alone. If one leg disappears, the drum still turns and the display still lights, but there is no heat. LG dryers detect this and show nP, which LG's help article explains as a power supply problem in which one of the two legs is not reaching the dryer. It is one of the few appliance codes that most often points outside the appliance.
Where a Leg Goes Missing
The dryer circuit is protected by a double-pole breaker, two linked switches in one body. One half can trip while the handle still looks on, or the handle can rest in a middle position that is neither on nor off. A loose connection at the breaker, at the receptacle behind the dryer, or at the terminal block where the cord enters the dryer can also drop a leg, and so can a cord that was fitted with the wrong terminal arrangement when the dryer was installed.
The Owner Check: the Breaker
Find the dryer breaker in the panel. Switch it fully off, then fully on, so both halves reset together. Return to the dryer and start a timed cycle with heat. If it now heats and the code is gone, a half-tripped breaker was the cause; if the breaker trips again in the next few days, something is drawing more than it should and that needs an electrician or a technician, not a habit of resetting it.
What Not to Do
Do not remove the cover over the terminal block on the back of the dryer, and do not pull the receptacle from the wall to look at it. Both carry 240 volts, the receptacle is live whether or not the dryer is plugged in, and testing them is meter work for someone trained to do it. If the breaker reset does not clear nP, the fault is in the receptacle, the cord, the terminal block or the dryer's own wiring, and the whole of that path is diagnosed with the breaker off and confirmed dead.
PS and Other Supply Messages
Some LG dryers show PS when the supply voltage is outside the range the control accepts, which can happen in a home with a marginal service connection or on a long circuit that sags under load. It shares a cause with nP often enough that the same breaker check applies first. On WashTower models the dryer half reports the same codes on its side of the shared panel.
Gas Dryers Are a Different Story
A gas dryer plugs into an ordinary 120-volt outlet and does not show nP for lack of heat. No heat on a gas model is an igniter, flame sensor or gas valve question inside the burner assembly, all of which are reached with the dryer unplugged and the gas shutoff valve closed, and none of which are owner parts. If you ever smell gas at a dryer, do not touch any switch or the dryer itself; leave the house and call the gas utility once you are outside.
Booking It
If a full off-and-on of the breaker does not clear nP, book an LG dryer repair and say whether the drum turns, whether the breaker had tripped, and how old the receptacle and cord are. A technician can confirm both legs at the terminal block and tell you within minutes whether the fault is the dryer or the circuit feeding it.