A:Answer Hi there,
I barely noticed a SPRING upon taking out the paper piece.
Mine fell on the floor and my dog almost got it.
It's inconvenient however because each time you finish unscrewing the pen cap, the spring falls. Sorry to say you may have lost the spring!
If you have the spring, try switching the way the spring sits in the pen, or the battery. I imagine it's one of the two making your pen unable to work.
Best of luck!