Hello @STELIANACONEAC
Thanks for posting this in the global Canvas community!
I understand that the +people button is missing in your course. There are a few reasons as to why that might be missing.
The option to add people to a course can be missing if the permission is not enabled/allowed for your TA role in the course. This is usually set up by your school's Canvas admin. If needed, they can reconfigure the role permissions you have in the course to allow for you to add users to a course. Some schools will use a SIS(student information system) to add users to courses. Sometimes that permission will be disabled due to that process.
The option to add people to a course can also go missing if the course has ended. (course settings) Since this is a new course, that would most likely not be the case.
For this, you would want to check with your school's Canvas account admin to see if they can allow you as a TA to add uses to courses.
Hopefully this helps!
-Colton