Issue with getting data via API with bearer token

Hi,

I am using an API that requires a bearer token embedded in the header that has a 30 min lifespan. I have constructed a Power Query ("M") that will pass the username and password to a Microsoft OWIN oauth token endpoint and this returns the required token correctly.

let
 url = #"Token URL",
 GetJson = Web.Contents(url,
     [
         Headers = [#"Accept"="application/json",
                    #"Content-Type"="application/x-www-form-urlencoded;charset=UTF-8"],
         Content = Text.ToBinary("username=XXXXXXX&password=XXXXXXXX&grant_type=password") 
     ]
 ),
 FormatAsJson = Json.Document(GetJson),

// Gets token from the Json response
 AccessToken = FormatAsJson[access_token],
 AccessTokenHeader = "bearer " & AccessToken,
 GetJsonQuery = Web.Contents(#"Search URL",
     [
         Headers = [#"Authorization"=AccessTokenHeader]
     ]
 ),
FormatAsJsonQuery = Json.Document(GetJsonQuery)
in
    #"FormatAsJsonQuery"

I then try to pass that token through to a Web.Contents function to process the API query with the authorisation token to pull the required data into Power BI.

On running this I get a prompt saying "Access to the resource is forbidden. Edit Credentials". So I try setting the credentials to anonymous but it keeps returning "Access is forbidden". This is probably due to the requirement of the "Authorization" key to pass the token. My assumption is Power BI then tries to intercept this and provide the authorisation prompt but this will not work for my requirement.

I know the token that is returned is working for authentication as I can use it externally from Power BI to run a GET query effectively, I just can't make this function inside Power BI.

Is there something I'm missing? Researching this proves fairly light on details and contradictory answers for this use case so if someone could clarify any experience it would be appreciated.

Thanks.