Postman API expense Post giving 401 unautherised error


I am trying to use postman to add expenses into freeagent -
Oauth 2 has been setup - this works fine when doing a get request - authentication works and i receive the JSON response with the required expense information.

Problem comes when i do a POST

I get error 401 authentication - This is using the same token as when doing a get which works fine so authentication should be fine.

Here is the JSON code i am using with the post to

{ “expenses”:

        "user": "",
        "category": "",
        "dated_on": "2018-07-10",
        "currency": "GBP",
        "gross_value": "-20.00",
        "native_gross_value": "-20.00",
        "sales_tax_rate": "20.0",
        "description": "Sundries"


anyone come across this problem before or am i missing something