About POL hens not laying - I've noticed that a lot of time hens are sold as POL when in fact they're as young as 12 or 14 weeks - much too young to start laying! I've also heard that if they're due to start laying at the beginning of winter or during winter, they often don't start until spring. Also if they're moulting, they don't lay.
There are lots of factors as to why a pullet mightn't be laying, but if you bought them as POL and they aren't laying yet, I would suggest that they weren't actually point of lay. I make a point to ask for the chicken's age in weeks on purchase rather than having someone tell me they're meant to start laying soon!