title: Not trying to use /Common endpoint, but Azure AD believes I am
body: <p>I'm using my organization's Azure AD to authenticate users on a corporate web app. I intend for this to be a single-tenant application. When I run it, I'm prompted to log in with my organization's credentials, as expected. On submitting my credentials, however, I get this error:</p>
  <blockquote>
  <p>Sorry, but we’re having trouble signing you in.</p>
  <p>AADSTS50194: Application '<em>appId</em>'(<em>appname</em>) is not configured as a multi-tenant application. Usage of the /common endpoint is not supported for such applications created after '10/15/2018'. Use a tenant-specific endpoint or configure the application to be multi-tenant.</p>
  </blockquote>
  <p>The thing is, <em>I'm not trying to use the /common endpoint.</em> Here is the relevant bit of my appsettings.json:</p>
  <pre><code>&quot;AzureAd&quot;: {
  &quot;Instance&quot;: &quot;https://login.microsoftonline.com/&quot;,
  &quot;Domain&quot;: &quot;COMPANYDOMAIN.onmicrosoft.com&quot;,
  &quot;TenantId&quot;: &quot;MYTENANTID-xxxx-xxxx-xxxx-xxxx&quot;,
  &quot;ClientId&quot;: &quot;MYCLIENTID-yyyy-yyyy-yyyy-yyyy&quot;,
  &quot;CallbackPath&quot;: &quot;/signin-oidc&quot;
  },
  </code></pre>
  <p>And here's the app's settings in the Azure portal (Home&gt;AppRegistrations&gt;App&gt;PlatformConfigurations&gt;Authentication):
  <a href="https://i.stack.imgur.com/MV3yy.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/MV3yy.png" alt="The app's Supported Account Types setting with 'Accounts in this organizational directory only' selected." /></a></p>
  <p>My startup.cs, which I assumed set the endpoint in question, is taken directly from the Microsoft-provided sample:</p>
  <pre><code>services.Configure&lt;OpenIdConnectOptions&gt;(AzureADDefaults.OpenIdScheme, options =&gt;
      {
          options.Authority = options.Authority + &quot;/v2.0/&quot;;
          options.TokenValidationParameters.ValidateIssuer = false;
      });
  </code></pre>
  <p>I've also set <code>false</code> to <code>true</code> for kicks, but the result was the same.</p>
  <p>What am I doing wrong, here? Why does Azure AD continue to believe I want to use the /common endpoint?</p>
  <hr />
  <p>Edit: As I continued to search, I happened on @jack-jia's answer here: <a href="https://stackoverflow.com/questions/57864036/application-is-not-configured-as-a-multi-tenant-application">Application is not configured as a multi-tenant application</a></p>
  <p>I haven't quite solved my issue, but their answer offered some promising clues.</p>