Not able to create / view tickets from AS API plugin

I am trying to create a plugin which can view / create / reply to tickets using your API. It was working all fine but only few days back. I am not able to access the tickets or create. I tried even with postman, zapier but failed. This is what I am getting in postman when trying to create ticket.

{
    "code": "rest_cannot_create",
    "message": "Sorry, you are not allowed to create tickets as this user.",
    "data": {
        "status": 401
    }
}

I am getting 401 even though the username and password is correct. The user hold the role of Support Agent.

When I tried using zapier I got similar un authorized error:
The app returned “Sorry, you are not allowed to create tickets as this user.”. Try reconnecting your account. This usually happens when we can’t connect to your account for an app or service because your password was changed or Zapier’s access was revoked.