Pyrotactics

Hi, I am new to 3D printing. Originally, I was using the Creality Slicer software that came with the Ender 3 Pro that I got, but for some reason it wasn't generating a gcode when I would try to slice something. As a result, I recently downloaded Cura. I have sliced several models and printed them no problem (though I did notice the slicing was a lot slower than the other software - previously slicing took a few seconds, now on Cura its taking a few minutes). This morning I tried to slice a model with the exact same setting as the last thing I printed, and now the slicer isn't moving past `30%. Layer height is 0.2mm and all the other setting looked fine. How can I fix this? Or how can I speed up the slicing process? Ideally I'd like to be back at the few seconds to slice.