some pumps dont allow the water to drain back through them, this could be your problem - though you didnt leave many details about your setup...
the basics are you have 2 holes in your tray:
1) typically a 1/2" connector and is called the fill/drain - your pump is hooked to this and when the pump shuts off the water drains back through the same line.
2) is the overflow and this is typically a 3/4" with a riser used to set the water level when you flood.
I bet that wetbac was a typo for wetvac :smiley_joint: