New Ceiling Light Fixture - No Voltage from box when attached?

Hi All, Newbie here looking for some help. I've replaced a few light fixtures lately with no problems at all, until this one. I'm getting a reading of 120v from hot to neutral, 120v from hot to ground and 0 from neutral to ground. Except when I connect the light fixture the voltages drop to 0. Forgive my complete lack of knowledge on the subject, but basically the light doesn't turn on. I've tested for resistance on the fixture itself and haven't encountered any issues, and also checked the voltage on the fixture itself (which reads 0). I also tried putting the old fixture back on that worked, but it's also experiencing the same issue. Any help would be greatly appreciated.