It can take a while, they may of developed but be the wrong way round & can't pip, I had that happen with my last lot (I like to open up and see what went wrong) hopefully they are just taking their time, they may of internally pipped, listen out for cheeping!
I'm hoping my 4 are ok, I'm expecting pipping today but nothing so far, may happen a bit later due to the plug incident or not atall grrr!
I've had great hatches from eBay eggs and selling my own, my last lot of light Sussex they hatched 6/6
Best of luck with your new gang!