I always candle once a week. This way you know what's happening as they develop. You wont dare get me to crack open a 3 week old rotten egg in my hand, had to many explode on me over the years, plus by this point usually you wouldnt see a ring or anything anyway, it will just be a rotten mess.
Also on shipped eggs, I always candle when they get here. Look at the air cell end on the big end of the egg. Lots of times, it will wiggle and roll around as it has been loosened from shipping vibrations. This is fine, usually 75%of these will still make it. BUT if it's not there (you should see a line where the cell is) and you see little bubbles floating freely around in the egg, then it was totally ruptured and dead, these will NEVER hatch or develop. Makes people ofthen thing they werent fertile, when in fact it was just damage internally.
NOW, that being said, yes it is totally possible this early in the year that they just werent fertile at all, or they may have froze over night once too.
The first few weeks of eggs from my bantam sumatras werent fertile either, the few I'm getting now are though....
Hate it though, wish you better luck in the future