It worked for me with a little trick, as the bulk course upload module have a bug even with the 2.9 version. If you can access your database just find out the actual id for the category you want to upload (id is an internal auto number assigned to category when we add a category) so upload your file with id not with idnumber which is user defined number. (Mysql/Mariadb sql command for knowing the actual id (select id,name from mdl_course_categories).