@JohnMburu
The advice you've gotten is correct. You need to contact your institution. I teach at a community college. When students register for classes through SIS, they are automatically added to our Canvas courses. We never send email invitations to students. In fact, that option is blocked.
1. Check with Admissions to make sure that you are, in fact, registered for this class.
2. If you are registered with SIS, then check with your school's IT help desk.
I'm sure that your instructor does not have the authorization to manually add students to their Canvas course. That's why you keep getting bounced out of it.
Good luck!