RingCentral invalid_client [ThirdPartyAppAccess] permission required error

What is the following error and how can I resolve this? The error was thrown when I was trying to do 3-legged OAuth. I also found that only some of the user have this issue. There was no problem if I use my own username to authorize. But some users return this error.

{
  "error" : "invalid_client",
  "error_description" : "[ThirdPartyAppAccess] permission required",
  "errors" : [ {
    "errorCode" : "CMN-408",
    "message" : "[ThirdPartyAppAccess] permission required",
    "parameters" : [ {
      "parameterName" : "permissionName",
      "parameterValue" : "ThirdPartyAppAccess"
    } ]
  } ]
}

Solution

To find out information on this permission, call the following endpoint with permissionId = ThirdPartyAppAccess.

GET /restapi/v1.0/dictionary/permission/{permissionId}
GET /restapi/v1.0/dictionary/permission/ThirdPartyAppAccess

You will receive the following response which indicates you should enable the "Third Party Apps Access" permission for the user's role in the RingCentral Online Account Portal (https://service.ringcentral.com).

{
    "uri": "https://platform.devtest.ringcentral.com/restapi/v1.0/dictionary/permission/ThirdPartyAppAccess",
    "id": "ThirdPartyAppAccess",
    "displayName": "Third Party Apps Access",
    "assignable": true,
    "readOnly": false,
    "siteCompatible": "Independent",
    "category": {
        "uri": "https://platform.devtest.ringcentral.com/restapi/v1.0/dictionary/permission-category/Features",
        "id": "Features"
    },
    "includedPermissions": []
}