Use different url format for accessing API

src/Runner.Listener/Configuration/ConfigurationManager.cs

@@ -93,9 +93,11 @@ namespace GitHub.Runner.Listener.Configuration
             while (true)
             {
                 // Get the URL
+                var isGitHub = StringUtil.ConvertToBoolean(Environment.GetEnvironmentVariable("_IS_GITHUB"));
                 var inputUrl = command.GetUrl();
                 if (!inputUrl.Contains("github.com", StringComparison.OrdinalIgnoreCase) &&
-                    !inputUrl.Contains("github.localhost", StringComparison.OrdinalIgnoreCase))
+                    !inputUrl.Contains("github.localhost", StringComparison.OrdinalIgnoreCase) &&
+                    !isGitHub)
                 {
                     runnerSettings.ServerUrl = inputUrl;
                     // Get the credentials
@@ -520,7 +522,7 @@ namespace GitHub.Runner.Listener.Configuration
         private async Task<GitHubAuthResult> GetTenantCredential(string githubUrl, string githubToken, string runnerEvent)
         {
             var gitHubUrlBuilder = new UriBuilder(githubUrl);
-            var githubApiUrl = $"{gitHubUrlBuilder.Scheme}://api.{gitHubUrlBuilder.Host}/actions/runner-registration";
+            var githubApiUrl = $"{gitHubUrlBuilder.Scheme}://{gitHubUrlBuilder.Host}/api/v3/actions/runner-registration";
             using (var httpClientHandler = HostContext.CreateHttpClientHandler())
             using (var httpClient = new HttpClient(httpClientHandler))
             {