Persistent access control exception error message on Moodle

I am trying to enroll a user on my Moodle site via using the Moodle API. My Moodle instance is hosted on AWS and all relevant ports are open and listening. So, from the network perspective, I can commit that is all ok. The steps I have already done based on Moodle Documentation: 1. I have enabled web services on `Administration > Mobile app >Mobile settings` 2. I have gone through the 10 steps on the overview of allowing an external system to control Moodle as explained in the documentation (shown also in [this Youtube video][1]) For testing purposes, I am using **Postman**. Some requests are going through (e.g. getting the token for a certain user, getting the list of all courses, etc.) Example: [![enter image description here][2]][2] But when I try to i.e. **create a user** or **enroll a user** in an existing course I am getting this error: { "exception": "webservice_access_exception", "errorcode": "accessexception", "message": "Access control exception" } The way I am trying to i.e. create the user is as follows: [![enter image description here][3]][3] In the body section I am sending the following data: - users[0][username] - users[0][email] - users[0][lastname] - users[0][firstname] - users[0][password] Based on my research, most of the contributors suggested enabling web services, but as mentioned above I have enabled them but the problem persists. Can someone help me solve the issue here or maybe suggest a way of debugging it? [1]: https://www.youtube.com/watch?v=KCNA5eo5q-Q [2]: https://i.sstatic.net/pV00R.png [3]: https://i.sstatic.net/YW5v5.png