A <CTRL+D> character on the first line of a trigger normally indicates the end of one job and the beginning of another. This prevents mixups in print jobs.
Some printers implement an Automatic Emulation Switching (Auto Switch) feature that automatically recognizes what emulation it requires to process a job. In this case, when the file containing your trigger is in ASCII, the printer does not recognize the first few lines as a PostScript program (your trigger). Instead it makes the printer enter ASCII emulation. To prevent this, you must modify the trigger as follows to force the printer to switch to PostScript.
<ESC>%-12345X
<ESC>%-12345X@PJL JOB
@PJL ENTER LANGUAGE = POSTSCRIPT
%!PS-Adobe
(INVOICE) run INVOICE