403 Current user cannot create courses [forbidden] while creating a course for Google classroom api (.Net) - google-classroom

Question

I have created a VisualStudio (C#) project, wihch use google classroom apis.
With Super admin, It can create a course, but with delegated admin, It returns an error.
I have use a delegated admin. Why does that error return ?
Errors [
Message[#UserCannotCreateCourse Current user cannot create courses.] Location[ - ] Reason[forbidden] Domain[global]
]
my code is below given
string[] Scopes = {ClassroomService.Scope.ClassroomCourses};
UserCredential credential;
using (var stream = new FileStream("credentials.json", FileMode.Open, FileAccess.Read))
{
string credPath = "token.json";
credential = GoogleWebAuthorizationBroker.AuthorizeAsync(
GoogleClientSecrets.Load(stream).Secrets,
Scopes,
"user",
CancellationToken.None,
new FileDataStore(credPath, true)).Result;
Console.WriteLine("Credential file saved to: " + credPath);
}
var service = new ClassroomService(new BaseClientService.Initializer()
{
HttpClientInitializer = credential,
ApplicationName = "Classroom test"
});
var body = new Course()
{
Name = "MyFirstClass",
OwnerId = "me"
};
var course = service.Courses.Create(body).Execute();
"credentials.json"File is from My Google Cloud Platform project.
My project is verificated.
./auth/classroom/courses
./auth/classroom/rosters
(etc.)
Delegated admin is created by Google Console.
I added custom admin role.

Answer 1

I found that the owner of the classroom course must a member of classroom_teachers Group. (If the account is not the super admin)
With an account that has not be a teacher, classroom api gets error.
And after becoming a teacher (manually sign-in, and create a classroom course), classroom api succeeded.
So, before creating a course, I join that account into classroom_teacher group.
Thank you.