Welcome to the front. The spline shape has to be closed for the shape to be extruded as a solid object.
One suggestion though. I think the handle would probably look nice and chunky if you made it from a box primitive. Using editable poly select and extrude some polygons to create the grooves in the hand grip and them turbosmooth the result. You cant turbosmooth an extruded shape succesfully so you are stuck with a hard edged handle if you use that method.

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Yeah, I agree with Tyson- Box modeling is probably the quickest way to a more interesting model, but if the assignment requires spline modeling as the base, then you could also use the Bevel modifier so it isn't quite so blocky.

Extrudes don't Cap for a few reasons- the splines need to be closed as Tyson said, none of the vertices broken (as is often the case with imported CAD files) and when the segments overlap because of Bezier Corner tangents (like sometimes happens in the crease of a heart shape)

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Thanks guys for the help, I knew that they had to be closed for it to work properly so I didn't instantly think that, that was causing the problems but I looked it over and saw that there was a small opening at the last point to where I started my path. So I just closed it off and it worked.

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