This does happen on occasion. Sometimes it is indicative of a faulty pump however the majority of the time it just means that there is a buildup of product stuck inside the pump. It's very easy to clean it out, just follow these steps:
Unscrew the lid and remove it from the bottle.
Take the top portion and run it under warm water while upside down.
Try pumping the top several times while under the water.
Keep pumping until the water has been worked through the pump and is coming out of the other side (this means the blockage is cleared).
After the blockage is cleared, dispel any water still left in the pump.
Allow the lid to dry and screw it back into the bottle with the product.
If you have followed all of these steps and the pump is still not working, please contact our customer service department HERE to receive a replacement pump.