It means there is an issue with the impeller. If the pump is under a year old please go to https://www.coralvue.com/support/submit_ticket and submit a ticket so one of our reps can help you troubleshoot and warranty the impeller if needed. If the pump is over a year old you will want to open up the pump and inspect the impeller for damage.
https://www.youtube.com/watch?v=TToz8HEYi8k