Internal Server Error - Creating Access Token

I am trying to create access token but I got the internal service error response. I have passed the exact endpoints  and tested it from different media i.e Postman, Laravel Package, and Mtn Developer Sandbox Request Sender

{

    "statusCode": 500,

    "message": "Internal server error",

    "activityId": "9b410efe-42f8-47fb-8292-55a86dbbb067"

}