What could cause a brand new fluorescent fixture to not work?
It's most likely just a defective ballast in the new fixture. Failure rate of course varies brand by brand, but none of them are immune to having a wonky ballast fly through the QA process.

I keep replacement ballasts around just like replacement lamps. Since they are rather cheap in most cases, I'd buy one (to test), then keep a small stock for the various types of fixtures that you have.