It is most likely because the waste bin is full. If so, remove and empty the waste bin. If the waste bin is not full, move the handle back and forth a few times to loosen the used B-Pod® to drop into the waste bin. Also, be sure you've removed the packing tape from the back of the waste bin so that it can fully open.
WARNING: There is a sharp needle inside the pod compartment. Do not insert your finger inside to remove the used B-Pod.