The following error may occur when the Maximum Worker Processes have been modified from the default value of 1 in Microsoft Dynamics CRM:

"Error: The Sandbox SDK Listener failed to start" - When attempt to navigate a recently imported Customization (with plugins) to a Dynamics CRM organization, it throws a following error:-

The Sandbox SDK Listener failed to start.
Source: w3wp.exe (3504)
Endpoint: net.tcp://localhost/CrmSandboxSdkListener-w3wp
Error: System.ServiceModel.AddressAlreadyInUseException: The TransportManager failed to listen on the supplied URI using the NetTcpPortSharing service: the URI is already registered with the service.


Modifying the IIS Maximum Worker Processes, otherwise known as Web Gardening, within the Microsoft Dynamics CRM Application Pool is not supported.


In IIS, right-click on Application Pool, select Advance Settings, and in the Process Model section, you will have “Maximum Worker Processes”. Edit the value to "1".

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