Loosing pressure -troubleshooting please- got the answer

[Europhyllia]

I got a Rio 2100 that I use to pump saltwater from the bug brute in the laundry room to the tanks in the dining room.
Today I couldn't pump. The pump came on when plugged in but couldn't get enough pressure to actually pump the water up and over the rim of the Brute.

I took it apart and tested it in the sink where - of course - it worked great and shot water across the room very efficiently

So. What might be the problem? Do I just need a new part or do I need a new pump?