I need some help figuring out what's wrong with my two new pumps. I bought them both from PexUniverse online. They shipped brand new. When I power them both up, they just hum. The fan in the back doesn't spin, neither does the magnet. I removed the head assembly to look at the magnet, and it won't spin with the head assembly removed. They have been both kept dry in my garage all summer. Is there some sort of locking pin they use during shipping that needs to be removed? Any suggestions?