XPS 15 F8 key won't respond to do factory image restore

Have an XPS 15 L501X I'm trying to clean up to part with. Have all my personal data off and uninstalled all software I added. Went to my Dell online manual to do the factory image restore, and the starting point was to tap F8 key when Dell logo appears, to access advanced boot options.. Have done this many times over the last 20 years with my Dell computers, usually F2 to access Setup. This computer works well when I hit F2 for setup and F12 for boot options. But it will not respond to the F8 key to bring up the Advance boot options needed to do the factory image. Have tried 30 or so times and it just continues on to loading windows. is there another way to access this screen, or something else I can try. I've had no other problems with computer. Ran the Dell hardware diagnostics and everything passed.. Loooked in the D partion and it appears the Dell image restore files are all there, I just can't access the F8 to get to them. I've made no changes or done anything with the D partition and the Hard drive is the original.