I'm not familiar with Onyx, however, it could just be that the SP-300V is too old of a printer and isn't compatible with the newer version of Onyx. I know for VersaWorks, the new 6 doesn't support the SP-300V. I have to use the old VW5 to use my SP-300V's, but run my newer VS-300i & SG-300 through 6. Just my 2 cents, as I've never used Onyx, I could be totally wrong.