There could be two causes of this message as follows:

1) The auger in the PCU will break causing toner not to be moved correctly in the unit. This problem is usually accompanied by a noise in the PCU area. The PCU assembly would need to be replaced.

2) The end-user is not pushing the hopper assembly fully in before latching the bottle latch. When this happens, you will find toner has leaked between the hopper and the toner bottle.