I had this exact same problem when I first got my HP plotter.
The fix is actually pretty simple, but really stupid.
For some reason, the HP plotter drivers need to be the first drivers installed. I had to de-install all printer drivers for all printers, including your HP and any other printer that may be installed.
Only install one HP driver, the one you plan on using. You mentioned you have an HP/GL2 card. Is this the physical card. If not, don't bother installing the HP/GL2 driver because it won't work, even if HP says it will.
After all drivers are uninstalled, install the HP driver(one only) first, restart your computer, and then install the drivers for any other printers you may have.
This worked for me.
Hope it works for you.
Grant