How long were they at room temp before you put them in the fridge? It wouldn't be unusual for a beer to need 2-3 weeks at >70°F in order to fully carbonate.
I'd get them back to room temp (or slightly warmer, 75-80°F, if you can), then invert them once or twice a day to get the yeast back in suspension. If there still isn't any carbonation after a week of that, then I'd re-yeast. 1 g rehydrated dry yeast per 5 gal is the rule of thumb.