Error in simulation of a DC/DC buck converter using LTspice
Yes. You are using a N-channel MOSFET as your switching element, and driving it with a signal that only goes to +5V.

The MOSFET is operating as a source-follower when it is on, and the output voltage can only rise as far as Vg - Vth, which in this case is only about 1.6 V

Either use a P-channel MOSFET, driven with a gate signal that is negative with respect to its source voltage (the supply voltage), or use a proper N-channel MOSFET driver that can drive the gate above the input voltage.

Note that if you had simply plotted the voltage across the diode, this would have been pretty obvious. I can never understand why people use simulators, and then don't take advantage of all the information they have to offer...