The only way to get no response is a broken connection somewhere along the way. So...
Multimeter: Test the ohms on your atty, and make sure that's still good. Then test the ohms from the firing pin to the center pin on the 510 connection of your grand. The new contacts in a grand test at .32 ohms, probably around .4 for the old contacts (unsure since I don't have the old contacts)... If those two test out fine, then it's a problem with the connection between you atty and the 510 on your grand...
Only other possibility would be the firing pin not touching the battery, which could be a few small things... But first that comes to mind might be a collapsed spring.
- Bboy