"Application cannot be started. Contact the application vendor" when run Microsoft 365 Desktop Setup


When you try to run a Microsoft 365 ClickOnce application such as Microsoft 365 Desktop Setup or the Microsoft 365 Desktop Readiness Tool, you receive the following error message:

Application cannot be started. Contact the application vendor.

Screenshot of the error message in the Cannot Start Application dialog box.

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 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

To check whether the problem is fixed, follow these steps:

More information

For more information, see ClickOnce Unmanaged API Reference.

Still need help? Go to the https://go.microsoft.com/fwlink/?linkid=2003907 website.