Bucket or carboy? Sometimes a ferm can happen in a bucket and enough gas escapes around the edge to keep the airlock silent.
If bucket, crack lid and look for signs of krausen around edge of wort/beer. If nothing, then more details on yeast, temps, volume, aeration, and gravity may yield clues for people to comment on and try to help. Some yeast are slow to start, but I'd think you'd have something by now.
A really slow or degraded ferm could occur from multiple small problems all adding up: old package, didn't rehydrate dry yeast, too cold, temps fluctuating at night, poor aeration, too-high gravity, etc.