Hi @sywang ...
The "Pending" label means that the student you manually enrolled has not yet accepted the invitation to the course. When a student signs in to Canvas (after you have manually added the student to the course), the student would get an e-mail notification and also see a course invite at the top of his/her Canvas Dashboard with a button to "Accept" the invitation.
I don't have tons of experience with this, so @mzimmerman may be of more help than I can be... but it sounds like you had uploaded the users via SIS import using something similar to the "users.csv" (under the "CSV Data Formats" header) format shown on this page? SIS Import Format Documentation - Canvas LMS REST API Documentation (instructure.com)
I *think* this would only batch upload the users...but not assign them to courses. If you scroll down a bit more on that page, there is an "enrollments.csv" table which gives the field names including the "course_id" and "user_id" (used from the "users.csv" file). I *think* you need to upload this file, too (?).
Again, I don't have tons of experience with this, but I have talked with someone in our IT department who handles our SIS uploads for courses, students, enrollments, etc., and I *think* this is what he typically does (if I remember correctly). Since users are added to courses via SIS import, then the "Pending" label you were asking about on the "People" page wouldn't show up...so it's not an issue any more.
If Mike Z. has a different way that this should be done (or if I've completely missed the boat on this), I'd be happy to be wrong...but I'll defer to him for a more help. Take care...
