Exchange 2016 - OWA opens but email preview pane just shows loading and no other menu options work either

The existing answer already covers the browser, OWA virtual directory and application pool checks.

If those look normal, I would trace one failed OWA request through the Exchange logs before changing anything else.

Check the same timestamp in:

• Frontend IIS log
• HttpProxy\Owa log
• Backend IIS log

Also use the browser Network tab to identify the request that remains pending or returns 4xx/5xx, then correlate that request with the Exchange logs.

This helps identify whether the request reaches the backend and where it starts failing.

I documented this troubleshooting method here: https://ceyhunkirmizitas.net/exchange-owa-authentication-troubleshooting-iis-logs-part-4/

Hi @Zameer Minhas

To help narrow this down, could you provide:

• Are you using OWA Light? The behavior described appears similar to the OWA Light experience documented by Microsoft. You can read more at Upcoming retirement of OWA Light in Exchange Server | Microsoft Community Hub.
• Which Exchange 2016 CU are you running?
• Does this affect all users or only specific mailboxes?
• Are there any errors in the browser Developer Console (F12) or Network tab when OWA hangs?
• Are there any relevant Application/MSExchange OWA events at the time the issue occurs?
• Is this a single Exchange server or a DAG/load-balanced environment?
• Did the issue begin after a recent Windows update, Exchange SU, certificate renewal, or IIS change?

Since ECP is working but OWA loads and then becomes unresponsive, the issue may be isolated to the OWA front end rather than Exchange services.

Here are a few things to check:

1.Browser-side issues

• Test in an InPrivate/Incognito window or a different browser.
• Clear the browser cache and cookies for the OWA site.
• Open Developer Tools (F12) and check the Console and Network tabs for JavaScript errors or failed requests.

2.OWA virtual directory health

• Verify the OWA virtual directory configuration:

    Get-OwaVirtualDirectory | fl Identity,InternalUrl,ExternalUrl,*Authentication*
  

• If the issue started after a certificate or authentication change, confirm the virtual directory settings are still correct.

3.IIS application pools

• Verify that MSExchangeOWAAppPool is running.
• Consider recycling the OWA application pool first. If necessary, perform an IIS reset during an appropriate maintenance window.

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