Imported Excel Spreadsheet not Filtering Column

I am uploading an excel template to the SharePoint site. I have 8 different metrics and want to add a filter to a specific column.SharePoint automatically adds the filter option to certain columns, but not all. The column I wish to add a filter to has just simple text (peoples names), but SharePoint does not add a filter to that column. Does anyone know how to add a filter or why SharePoint won’t filter?

Thanks in advance!