When connecting to Outlook Web App (OWA) for Exchange Server 2010 users may report the following error in their web browser.

Outlook Web App didn’t initialize. If the problem continues, please contact your helpdesk.
Couldn’t find a base theme (folder name=base)

This can be caused by missing OWA theme files in \ClientAccess\Owa\\themes sub-folder of the Exchange 2010 installation path. By default this is C:\Program Files\Microsoft\Exchange Server\V14\ClientAccess\Owa\\themes.

Exchange Server 2010 Error: Outlook Web App Didn't Initialize

To resolve the error you can perform a restore of the files to the Client Access server from a previous backup.

If that is not available to you then you can also restore the files by re-running Exchange Server 2010 SP1 setup in upgrade mode.

C:\Admin\Exchange2010SP1>setup /m:upgrade

Welcome to Microsoft Exchange Server 2010 Unattended Setup

Preparing Exchange Setup

    Copying Setup Files                           COMPLETED

The following server roles will be upgraded
Hub Transport Role
Client Access Role
Management Tools

Performing Microsoft Exchange Server Prerequisite Check

    Configuring Prerequisites                                 COMPLETED
    Language Pack Checks                                      COMPLETED
    Hub Transport Role Checks                                 COMPLETED
    Client Access Role Checks                                 COMPLETED

Configuring Microsoft Exchange Server

    Language Files                                            COMPLETED
    Restoring Services                                        COMPLETED
    Languages                                                 COMPLETED
    Hub Transport Server Role                                 COMPLETED
    Client Access Server Role                                 COMPLETED
    Exchange Management Tools                                 COMPLETED
    Finalizing Setup                                          COMPLETED

The Microsoft Exchange Server setup operation completed successfully.

You should now see the restored files in the correct location, and OWA will begin working again.

Exchange Server 2010 Error: Outlook Web App Didn't Initialize

About the Author

Paul Cunningham

Paul is a former Microsoft MVP for Office Apps and Services. He works as a consultant, writer, and trainer specializing in Office 365 and Exchange Server. Paul no longer writes for Practical365.com.


  1. downtobones

    Thanks Paul for this post, & thanks Ryan for the solution that worked for me, the setup /m:upgrade says “Copying files” but immediately finishes to the command prompt on my CU12 install.

  2. Ryan Rao

    Hi Paul,

    You can also run the following from EMS:

    C:Program FilesMicrosoftExchange ServerV14BinUpdateCas.ps1


  3. Lucas

    The Upgrade switch will overwrite modifications that were made on the Virtual Directories?

    1. Avatar photo
      Paul Cunningham

      Modifications such as…?

      Standard configs you’ve made via the EMC/EMS should be fine. Other customizations will probably be overwritten.

  4. Simon

    Thank you thank you thank you… this worked perfectly.

  5. Dinesh Silva

    Can we copy and paste it from a separate CAS installation or from a DR site?

    1. Avatar photo
      Paul Cunningham

      Probably yes. But if you’ve only got one CAS then that option wouldn’t be available 🙂

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