Need help with GE triton. I bought this house almost 2 years ago and had the dishwasher upgraded

Question

I bought this house almost 2 years ago and had the dishwasher upgraded to this model. We really haven't used it much in 18 months. Now I am ready to use it again, but when I start it, there is a horrible knocking sound under the sink. It only happens when it's trying to fill. Any help would be appreciated!Thanks!Cathy