i'm getting 403 error using the ip loopback

[Cariaga]

it says "Success, you can return to the app now!" but this pops up
but the part in

 var payLoad =
            $"{{\"postBody\":\"id_token={token}&providerId={providerId}\",\"requestUri\":\"http://localhost\",\"returnIdpCredential\":true,\"returnSecureToken\":true}}";
        RestClient.Post($"https://identitytoolkit.googleapis.com/v1/accounts:signInWithIdp?key={ApiKey}", payLoad).Then(
            response =>
            {
                // You now have the userId (localId) and the idToken of the user!
                Debug.Log(response.Text);
           }).Catch(Debug.Log);    
    }

RequestException: HTTP/1.1 403 Forbidden
UnityEngine.Debug:LogError (object)
FirebaseAuthHandler/<>c:<SingInWithToken>b__1_1 (System.Exception) (at Assets/Scripts/FirebaseAuthHandler.cs:27)
RSG.Promise/<>c__DisplayClass44_0:<Catch>b__1 (System.Exception) (at Assets/RestClient/Packages/RSG.Promise/Promise_NonGeneric.cs:660)
RSG.Promise:InvokeRejectHandler (System.Action`1<System.Exception>,RSG.IRejectable,System.Exception) (at Assets/RestClient/Packages/RSG.Promise/Promise_NonGeneric.cs:437)
RSG.Promise/<>c__DisplayClass34_0:<InvokeRejectHandlers>b__0 (RSG.RejectHandler) (at Assets/RestClient/Packages/RSG.Promise/Promise_NonGeneric.cs:500)
RSG.Promises.EnumerableExt:Each<RSG.RejectHandler> (System.Collections.Generic.IEnumerable`1<RSG.RejectHandler>,System.Action`1<RSG.RejectHandler>) (at Assets/RestClient/Packages/RSG.Promise/EnumerableExt.cs:15)
RSG.Promise:InvokeRejectHandlers (System.Exception) (at Assets/RestClient/Packages/RSG.Promise/Promise_NonGeneric.cs:500)
RSG.Promise:Reject (System.Exception) (at Assets/RestClient/Packages/RSG.Promise/Promise_NonGeneric.cs:554)
RSG.Promise`1/<>c__DisplayClass44_0<Proyecto26.ResponseHelper>:<Then>b__1 (System.Exception) (at Assets/RestClient/Packages/RSG.Promise/Promise.cs:767)
RSG.Promise`1<Proyecto26.ResponseHelper>:InvokeHandler<System.Exception> (System.Action`1<System.Exception>,RSG.IRejectable,System.Exception) (at Assets/RestClient/Packages/RSG.Promise/Promise.cs:353)
RSG.Promise`1/<>c__DisplayClass24_0<Proyecto26.ResponseHelper>:<InvokeRejectHandlers>b__0 (RSG.RejectHandler) (at Assets/RestClient/Packages/RSG.Promise/Promise.cs:381)
RSG.Promises.EnumerableExt:Each<RSG.RejectHandler> (System.Collections.Generic.IEnumerable`1<RSG.RejectHandler>,System.Action`1<RSG.RejectHandler>) (at Assets/RestClient/Packages/RSG.Promise/EnumerableExt.cs:15)
RSG.Promise`1<Proyecto26.ResponseHelper>:InvokeRejectHandlers (System.Exception) (at Assets/RestClient/Packages/RSG.Promise/Promise.cs:381)
RSG.Promise`1<Proyecto26.ResponseHelper>:Reject (System.Exception) (at Assets/RestClient/Packages/RSG.Promise/Promise.cs:437)
Proyecto26.RestClient:Promisify<Proyecto26.ResponseHelper> (RSG.Promise`1<Proyecto26.ResponseHelper>,Proyecto26.RequestException,Proyecto26.ResponseHelper) (at Assets/RestClient/Packages/Proyecto26.RestClient/RestClientPromise.cs:341)
Proyecto26.HttpBase/<CreateRequestAndRetry>d__0:MoveNext () (at Assets/RestClient/Packages/Proyecto26.RestClient/Helpers/HttpBase.cs:40)
UnityEngine.SetupCoroutine:InvokeMoveNext (System.Collections.IEnumerator,intptr)