Refresh fails for Custom Api datasource

Hi v-zhangti ,

Thank you for your time and help. I followed the first link and created custom connector when i try to load that into power bi. It pops up with the following error.

Am i missing something here ?

// This file contains your Data Connector logic
section Testingproject;

// TODO: add your client id and secret to the embedded files

client_id = "xxx";
client_secret = "xxx";

redirect_uri = "https://oauth.powerbi.com/views/oauthredirect.html";
windowWidth = 800;
windowHeight = 800;
logout_uri = "https://login.microsoftonline.com/logout.srf";
BaseUrl = "https://xxxxxxxx/reporting-xxxxx/stats";
OAuthBaseUrl = "https://xxxx.okta.com/oauth2/xxxxx/v1/token";

// OAuth2 scope
scopes = {
    "/service/xxxxxx.Dashboard.read"
};

[DataSource.Kind="Testingproject", Publish="Testingproject.Publish"]
shared Testingproject.Contents = (url as text) =>
    let
        token = Extension.CurrentCredential()[access_token],
      
       headers = [Authorization = "Bearer " & token],
       Report = Json.Document(Web.Contents(url, [Headers = [#"Content-Type" = "application/json", Authorization=headers]]))
    in
       
        Report;

// Data Source Kind description
Testingproject = [
    TestConnection = (dataSourcePath) => { "Testingproject.Contents", dataSourcePath },
    Authentication = [
        OAuth = [
            StartLogin = StartLogin,
            FinishLogin = FinishLogin,
            Refresh = Refresh,
            Logout=Logout
        ]
    ],
    Label = Extension.LoadString("DataSourceLabel")
];

// Data Source UI publishing description
Testingproject.Publish = [
    Beta = true,
    Category = "Other",
    ButtonText = { Extension.LoadString("ButtonTitle"), Extension.LoadString("ButtonHelp") },
    LearnMoreUrl = "https://powerbi.microsoft.com/",
    SourceImage = Testingproject.Icons,
    SourceTypeImage = Testingproject.Icons
];

StartLogin = (resourceUrl, state, display) =>
    let
        AuthorizeUrl = OAuthBaseUrl
            & "?"
            & Uri.BuildQueryString(
                [
                    client_id = client_id,
                    response_type = "code",
                    state = state,
                    redirect_uri = redirect_uri,
                    scope = scopes
                ]
            )
    in
        [
            LoginUri = AuthorizeUrl,
            CallbackUri = redirect_uri,
            WindowHeight = windowHeight,
            WindowWidth = windowWidth,
            Context = null
        ];


FinishLogin = (context, callbackUri, state) =>
    let
        parts = Uri.Parts(callbackUri)[Query],

        result = if (Record.HasFields(parts, {"error", "error_description"})) then 
                    error Error.Record(parts[error], parts[error_description], parts)
                 else
                    TokenMethod("code", parts[code])
    in
        result;

Refresh = (resourceUrl, refresh_token) => TokenMethod("refresh_token", "refresh_token", refresh_token);

Logout = (token) => logout_uri;

TokenMethod = (tokenField, code) =>
    let
        tokenResponse = Web.Contents(
            OAuthBaseUrl,
            [
                Content = Text.ToBinary(
                    Uri.BuildQueryString(
                        [
                            client_id = client_id,
                            client_secret = client_secret,
                            code = code,
                            scope = scopes,
                            grant_type = "client_credentials",
                            redirect_uri = redirect_uri
                        ]
                    )
                ),
                Headers = [#"Content-type" = "application/x-www-form-urlencoded", #"Accept" = "application/json"]
            ]
        ),
        body = Json.Document(tokenResponse),
        result = if (Record.HasFields(body, {"error", "error_description"})) then 
                    error Error.Record(body[error], body[error_description], body)
                 else
                    body
    in
        result;

Testingproject.Icons = [
    Icon16 = { Extension.Contents("Testingproject16.png"), Extension.Contents("Testingproject20.png"), Extension.Contents("Testingproject24.png"), Extension.Contents("Testingproject32.png") },
    Icon32 = { Extension.Contents("Testingproject32.png"), Extension.Contents("Testingproject40.png"), Extension.Contents("Testingproject48.png"), Extension.Contents("Testingproject64.png") }
];

I am new to this mquery functionality. Could you please take a look and let me know what i am missing over here?