title: Why switch to Azure Web app / API to Multi-tenanted is not working?
body: <p>I have a <code>Web app / API</code> deployed on <code>Microsoft Azure</code> working in single tenant mode. I need to enable users from other tenants to be able to use my API. </p>
  
  <p>I found this post with step-by-step guide to enable multi-tenant authentication, 
  <a href="https://blog.mastykarz.nl/configuring-multi-tenant-authentication-azure-app-service-authentication-options/" rel="nofollow noreferrer">https://blog.mastykarz.nl/configuring-multi-tenant-authentication-azure-app-service-authentication-options/</a></p>
  
  <p>but when I try to change Web API's <code>Multitenanted</code> property to Yes, it says "failed to update App ID URI application property" with following error detail:</p>
  
  <pre><code>{"errorCode":"HostNameNotOnVerifiedDomain","localizedErrorDetails":
  {"errorDetail":"Host name in property identifierUris is not on any verified
   domain of the company or its subdomain."},
  "operationResults":null,"timeStampUtc":"2017-01-11T00:14:37.3270764Z",
  "clientRequestId":"...","internalTransactionId":"...",
  "upn":"...@gmail.com","tenantId":"...","userObjectId":"..."}
  </code></pre>
  
  <p>Currently App ID URI holds address of my Web API (and it is working in single tenant mode as expected) <code>https://(..).azurewebsites.net</code> is this not correct for multi tenanted mode?</p>