Bios options greyed out

Hello. I have a HP 800 G1. I can not get it to run on onboard graphics. I activate the onboard graphics in the bios setup and save the configuration but when I boot without a graphics card it doesn’t display. I have tried resetting the CMOS using the onboard reset button as per the manual. I have tried leaving the battery out all night. I have updated the bios to the latest version. There is an option for VGA options in the bios setup menu but it is greyed out and can not be accessed. The onboard video used to work before I put a card in. Is there a modded bios available for this model in a form that can be flashed normally? (dos or windows flash). Thank you all for your time and attention. I appreciate it.