403, The caller does not have permission, when try to get a test token

Question

I try use get a test token following this instruction https://developers.google.com/identity/protocols/risc#java_3, and I get `

 "code": 403,
        "message": "The caller does not have permission",
        "status": "PERMISSION_DENIED"

`

When I register my endpoint, it return 200, so the register is success. I enable risc api for my project, and grant admin role. Is there any other things should I try?