As others have commented, the pump fails after a period of time.  I'm on my 3 in 4 years and just put in a claim for a 4th.  It will lose suction power to draw soap from the bottle and stop working.  Soaking it or other troubleshooting will not fix it.  It's a design flaw.  The good news is that it has a lifetime warranty.  If they won't solve the issue and manufacturer a better one, they'll just continue to send you new ones.  I'd rather not go through the hassle.