Buck Converter EMI simulation output LTSpice
When drawing the LISN into your schematic you have to decide where you are placing your GND symbol.
I notice that you have a GND symbol at the bottom of V1 and also in the center of the LISN.  That's not correct because C4 and R5 are connected to GND at both ends.
Also remember that (as things are drawn right now) the reference point for your &quot;out&quot; node is node &quot;n&quot; rather than ground.  So to get the supply output voltage you must measure V(out) - V(n) rather than just V(out) relative to ground.