Exchange 2019 OWA won't open

Question

Hi,

Since we updated to CU12 ont Exchange 2019 (on-premise), we have a problem with OWA web page.

When you connect to https://exchange_server/owa, you get the usual login prompt but when you login, you get this error :

I already restarted IIS, the server and the OWA Apppool and it doesn't change anything.

I found this warning that seems related : Event 1309

Event code: 3005 
Event message: Une exception non gérée s'est produite. 
Event time: 22/05/2023 11:22:49 
Event time (UTC): 22/05/2023 09:22:49 
Event ID: b4c02baf3b864817b79fe700208433f4 
Event sequence: 2 
Event occurrence: 1 
Event detail code: 0 
 
Application information: 
    Application domain: /LM/W3SVC/2/ROOT/owa-3-133292209494883356 
    Trust level: Full 
    Application Virtual Path: /owa 
    Application Path: E:\EXCHANGE\ClientAccess\owa\ 
    Machine name: SRVMAIL2019 
 
Process information: 
    Process ID: 7076 
    Process name: w3wp.exe 
    Account name: AUTORITE NT\Système 
 
Exception information: 
    Exception type: ArgumentException 
    Exception message: Un élément avec la même clé a déjà été ajouté.
   à System.ThrowHelper.ThrowArgumentException(ExceptionResource resource)
   à System.Collections.Generic.Dictionary`2.Insert(TKey key, TValue value, Boolean add)
   à Microsoft.Exchange.Clients.Owa.Core.OwaSettingsLoaderBase.InitializeLocalVersionFolders()
   à Microsoft.Exchange.Clients.Owa.Core.OwaSettingsLoaderBase.Load()
   à Microsoft.Exchange.Clients.Owa.Core.OwaSettingsLoader.Load()
   à Microsoft.Exchange.Clients.Owa.Core.OwaApplicationBase.ExecuteApplicationStart(Object sender, EventArgs e)
   à Microsoft.Exchange.Clients.Owa.Core.OwaModule.Init(HttpApplication context)
   à System.Web.HttpApplication.RegisterEventSubscriptionsWithIIS(IntPtr appContext, HttpContext context, MethodInfo[] handlers)
   à System.Web.HttpApplication.InitSpecial(HttpApplicationState state, MethodInfo[] handlers, IntPtr appContext, HttpContext context)
   à System.Web.HttpApplicationFactory.GetSpecialApplicationInstance(IntPtr appContext, HttpContext context)
   à System.Web.Hosting.PipelineRuntime.InitializeApplication(IntPtr appContext)

 
 
Request information: 
    Request URL: https://localhost:444/owa/exhealth.check 
    Request path: /owa/exhealth.check 
    User host address: ::1 
    User:  
    Is authenticated: False 
    Authentication Type:  
    Thread account name: AUTORITE NT\Système 
 
Thread information: 
    Thread ID: 25 
    Thread account name: AUTORITE NT\Système 
    Is impersonating: False 
    Stack trace:    à System.ThrowHelper.ThrowArgumentException(ExceptionResource resource)
   à System.Collections.Generic.Dictionary`2.Insert(TKey key, TValue value, Boolean add)
   à Microsoft.Exchange.Clients.Owa.Core.OwaSettingsLoaderBase.InitializeLocalVersionFolders()
   à Microsoft.Exchange.Clients.Owa.Core.OwaSettingsLoaderBase.Load()
   à Microsoft.Exchange.Clients.Owa.Core.OwaSettingsLoader.Load()
   à Microsoft.Exchange.Clients.Owa.Core.OwaApplicationBase.ExecuteApplicationStart(Object sender, EventArgs e)
   à Microsoft.Exchange.Clients.Owa.Core.OwaModule.Init(HttpApplication context)
   à System.Web.HttpApplication.RegisterEventSubscriptionsWithIIS(IntPtr appContext, HttpContext context, MethodInfo[] handlers)
   à System.Web.HttpApplication.InitSpecial(HttpApplicationState state, MethodInfo[] handlers, IntPtr appContext, HttpContext context)
   à System.Web.HttpApplicationFactory.GetSpecialApplicationInstance(IntPtr appContext, HttpContext context)
   à System.Web.Hosting.PipelineRuntime.InitializeApplication(IntPtr appContext)
 
 
Custom event details: 

Yet I don't find a solution, do you have an idea ?

ECP works fine.

Answer 1

Hi @Baudet Denis ,

I've tried searching a lot but can hardly find information about OWA issues related to the exact same event details. But I assume it's worth trying to regenerating the SharedWebConfig.config file by following the instructions in the link below:
(If there's already a SharedWebConfig.config file in the mentioned locations, you can rename or move to another location beforehand as a backup)

Can't access EAC or OWA after Exchange installation

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Answer 2

Ensure the backend site SSL is the self-signed Exchange Server cert and not your trusted one.

https://docs.microsoft.com/en-us/exchange/troubleshoot/client-connectivity/exchange-security-update-issues

Also check this article for more insight - https://learn.microsoft.com/en-us/exchange/troubleshoot/client-connectivity/owa-stops-working-after-update

Answer 3

Problem seems fixed by installing KB5019758

Hi @Baudet Denis ,

Great to know that the issue has been resolved and thanks for the share so that others experiencing the same thing can easily reference this! Since the Microsoft Q&A community has a policy that "The question author cannot accept their own answer. They can only accept answers by others", I'll repost your solution in case you'd like to "Accept" the answer : )

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[Exchange 2019 OWA won't open]

Issue Symptom:

Cannot open OWA since updating to CU12 on Exchange 2019 (on-premise).
Already restarted IIS, the server and the OWA App pool and it doesn't change anything.

Event 1309 with the following Exception information

    Exception type: ArgumentException 
    Exception message: Un élément avec la même clé a déjà été ajouté.
   à System.ThrowHelper.ThrowArgumentException(ExceptionResource resource)
   à System.Collections.Generic.Dictionary`2.Insert(TKey key, TValue value, Boolean add)
   à Microsoft.Exchange.Clients.Owa.Core.OwaSettingsLoaderBase.InitializeLocalVersionFolders()
   à Microsoft.Exchange.Clients.Owa.Core.OwaSettingsLoaderBase.Load()
   à Microsoft.Exchange.Clients.Owa.Core.OwaSettingsLoader.Load()
   à Microsoft.Exchange.Clients.Owa.Core.OwaApplicationBase.ExecuteApplicationStart(Object sender, EventArgs e)
   à Microsoft.Exchange.Clients.Owa.Core.OwaModule.Init(HttpApplication context)
   à System.Web.HttpApplication.RegisterEventSubscriptionsWithIIS(IntPtr appContext, HttpContext context, MethodInfo[] handlers)
   à System.Web.HttpApplication.InitSpecial(HttpApplicationState state, MethodInfo[] handlers, IntPtr appContext, HttpContext context)
   à System.Web.HttpApplicationFactory.GetSpecialApplicationInstance(IntPtr appContext, HttpContext context)
   à System.Web.Hosting.PipelineRuntime.InitializeApplication(IntPtr appContext)

Resolution:

Install KB5019758.