Unable to push file to git repository

using (var repo = GetGitRepo())
{
    // clean remote by remove and re-add
    var remoteName = Settings.GetSetting(Constants.GitUsername);
    repo.Network.Remotes.Remove(remoteName);
    Remote remote = repo.Network.Remotes.Add(remoteName, Settings.GetSetting(Constants.GitServer));

    // build credentials to repo in PushOptions        
    var options = new PushOptions();
    options.CredentialsProvider = new CredentialsHandler(
                    (_url, _user, _cred) =>
                        new UsernamePasswordCredentials() { Username =   Settings.GetSetting(Constants.GitUsername), Password =   Settings.GetSetting(Constants.GitPassword) });

    var pushRefSpec = _workingBranch.CanonicalName;

    repo.Network.Push(remote, pushRefSpec, options);
}

"credsStore": "whatever"

gcloud docker ...