Brand new Catit daisy fountain pump making buzzing sound

I bought a new pump for my Catit fountain, and it's already making a buzzing sound after two days of running. It's not blocked, dirty, or improperly assembled. I took it out and took it apart and put it back together and it stopped for about a day but now it's doing the same thing again. Has anyone else had this happen? Is it a faulty pump? Water level isn't low. The fountain is scrubbed clean and the water and filter are new and clean.