Have you tried using the HP driver instead: use the Print Command to access system or OS level printer drivers such as the one supplied with your plotter as Plot simply invokes a Graphisoft supplied driver.
If this works, establish this as the method for printing. HP drivers for the 500 give different printable areas for virtually everything - including the same sheet sizes in portrait or landscape mode.
I found this very vexing when trying to set up office standards and titleblocks.
Think Like a Spec Writer
MacBook M4Pro
AC4.55 through 29 / AC29.0.1 USA
Rhino 8.25 Mac
MacOS Tahoe 26.1