Community
I don't have any bright ideas about why it doesn't work if it used to, though I wonder whether the (princ) does anything for you [exiting a Close command "quietly" doesn't seem necessary, since you're getting out of the drawing]. But since it looks like it's just a shortcut way of getting the regular Close command anyway, you could add a line such as:
CX, *CLOSE
to your ACAD.PGP file, and make it a command alias, just like L for Line, etc. Then it ought to behave just as if you typed in the entire word CLOSE [assuming doing it that way still lets you type the Y normally].