especially dandelions, is a full day or two after a rain when the ground just starts to firm-up again. If the soil is too hard your weeding tool is going to difficulty penetrating the soil. If the ground is too soft the bottom plate will have nothing to push against to drive the shaft upward to engage the trigger mechaniism. The goal is to have just enough resistance, when stepping on the pedestal, to permit the center shaft to travel 3-4 clicks on the against the trigger.
If the soil is too damp it will compact against the tines, this causes the shaft to bind slightly. Tapping the base on the ground lightly loosens the soil enough to be ejected, in most cases. Clay, pebbles and twigs may also cause the tool to bind, rarely does it require the operator to manually eject the weed with the "manual ejector". If this occurs too often then postpone your weeding for another day.