So you mean is doesn't run when you plug it in? Are you sure the impeller
isn't jammed with something? Does it hum or get warm when plugged in?
Stone cold means it probably is dead.

When I plug it in nothing happens. It's hard to get to without being
in the water, and I don't want to accidently get fried by the pump so
I don't want to go in there with it plugged in. I did visually check
the intake just to verify that it wasn't clogged, one time I
accidently knocked off the inflow tube to the filter and it was
clogged with hornwort particles but it seems clear now. I might try
pushing water into the filter from the output just to see if anything
comes up but I think it's dead. It has an ouput fountain projecting
out of the filter and it doesn't even budge when I plug in the power.