Oauth Google Classroom API Problem (JAVA)

I need help with the google classroom API. I can create courses without problem, but when i want to assign teacher or enroll students i have a problem: [login to view URL]: 403 Forbidden { "code" : 403, "errors" : [ { "domain" : "global", "message" : "The caller does not have permission", "reason" : "forbidden" } ], "message" : "The caller does not have permission", "status" : "PERMISSION_DENIED" }