If you buy a bottle of hand soap, lotion, or other pump dispenser item, sometimes the plunger dispenser is locked down so it won't accidentally squirt while being transported.
To unlock the plunger, hold the bottle and twist the plunger counterclockwise until it pops up.
Occasionally, the plunger will rotate but not pop up. To remedy this, unscrew the plunger from the bottle and remove it. Wipe the soap or lotion off the stem. Grasp the stem in one hand and the plunger in the other hand and twist it counterclockwise.
This remedy is a bit messy, but it's simple.