Thank you all for your answers. It turns out the list needed to be cleaned up first and now I was able to upload the whole thing.
However, now there is a new problem. The Excel file has 20,395 entries. The file itself continues for thousands of empty rows. When I uploaded the fixed file I was expecting to have 20,395 names. Instead, the upload copied all of the blank fields as well. I now currently have tens of thousands of blank entries in my list. How do I remove them?