PROBLEM
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: 
When you click Details, you receive a detailed error message that resembles the following:
Application cannot be started. Contact the application vendor.
ERROR SUMMARY
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.
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.
CAUSE
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.
SOLUTION
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.
For Windows 8
For Windows 7, Windows Vista, Windows XP, Windows Server 2008 or Windows Server 2003
Notes
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
For Windows 7, Windows Vista, Windows XP, Windows Server 2008 or Windows Server 2003
Notes
- 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.
Let me fix it myself
To clear the ClickOnce application cache, follow these steps:- Click Start, click Run, type cmd, and then click OK.
- Type the following command, and then press Enter: rundll32 dfshim CleanOnlineAppCache
- Check whether the problem is fixed.
- If the problem is fixed, you are finished with these steps.
- If the problem is not fixed, visit https://go.microsoft.com/fwlink/?linkid=2003907 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.
MORE INFORMATION
For more information, visit the following Microsoft website:
Still need help? Go to the https://go.microsoft.com/fwlink/?linkid=2003907 website.