Hi David,
URL : {baseurl}/oxauth/restv1/introspection
Method: POST
Header: 
Authorization:Bearer bf6d4b7a-a4a5-4738-8b69-3db02f45684e
Content-Type:application/x-www-form-urlencoded
Request:
 
token:bf6d4b7a-a4a5-4738-8b69-3db02f45684e
token_type_hint:access_token
scope:uma_protection
Response:
{
    "active": true,
    "scopes": [
        "openid",
        "profile",
        "uma_protection",
        "externalId",
        "email"
    ],
    "client_id": "xxxx",
    "username": "kesavan",
    "token_type": "bearer",
    "exp": 1518588745545,
    "iat": 1518588445545,
    "sub": null,
    "aud": "xxx",
    "iss": "",
    "jti": null,
    "acr_values": null
}
I got a success response. before i am also getting error response like access denied
I found the issue, our main issue is we are not using access token as bearer in authorizatiion header and also use scope = uma_protection 
use Both Bearer token and input reguest token as same 
Thanks 
Kesavan