Not getting Refresh token in generate Access token response

{

    "access_token": "--------",

    "expires_in": 4215,

    "restricted_to": [],

    "token_type": "bearer"

}

 

Request is this- https://api.box.com/oauth2/token

Client-

client_secret-

grant type-

code- (code i am using the one we get in Authorize response)

 

And when i am using the access token generated above, for any subsequent api like Get user, i am getting invalid or missing access token.

 

Please suggest what am i missing here.