Good evening Parting line and parting plane can be created on the polygon model, but you do need a solid model to use the Volumes/Core/Footprint function. On the other hand, it has a problem on your model when defining the joint line. Everything goes smoothly by selecting the large flat base to define this joint line and the opening direction. But after validation, if we re-edit this function, the surface retained by SolidWorks is one of the oblique triangular faces. And it is impossible to make him listen to reason.
My solution: remove the two functions of line and parting line, and start from scratch their definitions... It works, and both parts of the mold can be generated.