Yeah, just wait it out. 3 weeks is my minimum for perfect carbing, before I start thinking anything may be wrong (conditioning can take longer though). Not to say I don't try some at two weeks every now and then. Also, make sure you put them in the fridge for at least 24-48 hours beforehand. You can't just do a 30 minute chill. CO2 dissolves into the beer better at cold temperatures, so if you don't give it some fridge time, they can seem undercarbed. The CO2 will be in the bottle, but mostly in the neck.
You'd really have to try to get all the yeast out of there so they wouldn't carb at all. If you have less yeast in the bottle, then it can just take longer, but eventually they'll carb up. Also, bigger beers can take longer to carb, because the yeast can be stressed.