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Article ID: 2697990 - Last Review: October 6, 2014 - Revision: 20.0

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When you try to run a Microsoft Office 365 ClickOnce application such as Office 365 Desktop Setup or the Office 365 Desktop Readiness Tool, you receive the following error message:
Application cannot be started. Contact the application vendor.
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A screen shot of the Cannot Start Application dialog box, showing the error message
When you click Details, you receive a detailed error message that resembles the following:
Below is a summary of the errors, details of these errors are listed later in the log.
* Activation of https://<NameOfDomain>/ClickOnceConnector/Office365DesktopSetup.application resulted in exception. Following failure messages were detected:
+ Unable to install this application because an application with the same identity is already installed. To install this application, either modify the manifest version for this application or uninstall the preexisting application.


This issue occurs if the application was cached in the ClickOnce application cache. The application must be removed from the cache before you can successfully run it.


To have us fix the problem for you, go to the "Fix it for me" section. If you prefer to fix this problem yourself, go to the "Let me fix it myself" section.

Fix it for me

To clear the ClickOnce application cache automatically, click the Fix it button or link. Then click Run in the File Download dialog box, and follow the steps in the Fix it wizard.

For Windows 8

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Fix this problem (
Microsoft Fix it 20050
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For Windows 7, Windows Vista, Windows XP, Windows Server 2008 or Windows Server 2003

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Fix this problem (
Microsoft Fix it 50934
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  • This wizard may be in English only. However, the automatic fix also works for other language versions of Windows.
  • If you are not on the computer that has the problem, save the Fix it solution to a flash drive or a CD, and then run it on the computer that has the problem.
Then, go to the "Did this fix the problem?" section.

Let me fix it myself

To clear the ClickOnce application cache, follow these steps:
  1. Click Start, click Run, type cmd, and then click OK.
  2. Type the following command, and then press Enter:
    rundll32 dfshim CleanOnlineAppCache
Did this fix the problem?
  • Check whether the problem is fixed.
    • If the problem is fixed, you are finished with these steps.
    • If the problem is not fixed, visit the Office 365 Community website ( or contact support ( .
  • We would appreciate your feedback. To provide feedback or to report any issues with this solution, please leave a comment on the "Fix it for me ( " blog or send us an email ( message.


For more information, visit the following Microsoft website:
ClickOnce Unmanaged API Reference (

Still need help? Go to the Office 365 Community ( website.

Applies to
  • Microsoft Office 365
  • Microsoft Office 365 ProPlus
  • Microsoft Windows XP Professional
  • Microsoft Windows XP Home Edition
  • Office 365 User and Domain Management
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