Is that stock D76? Try it at 1+1 for about 9:00 or 10:00 for greater economy and less solvent effect (sharper grain).
Even with gross (4 stops) overexposure, you should still see an image on the negative. Perhaps you accidentally exposed the first three sheets to daylight? Easy mistake to make when starting out.
What did the lightmeter say for these exposure tests? If you're not sure of your exposure, try making some test exposures in Sunny-16 lighting (full direct sun). f/16 at t=1/ISO is the right exposure (assuming you're focused near infinity therefore no bellows correction required), so try f/22 1/30s for EI60, which is a good speed for the Arista 100.