The plug-in execution failed because no Sandbox Hosts are currently available.

You have successfully implemented CRM servers and expect your Sandbox service to execute plugins in Isolation mode; however, they fail with an error:

ERROR:
The plug-in execution failed because no Sandbox Hosts are currently available. Please check that you have a Sandbox server configured and that it is running. System.ServiceModel.EndpointNotFoundException: Microsoft Dynamics CRM has experienced an error. Reference number for administrators or support: #357E9BEE

Possible Causes:

• CRM Sandbox service is not running
• CRM Sandbox ports are unavailable on the sandbox server
• CRM Sandbox service is missing SPN's
• CRM Sandbox is remote and the CRM Services cannot be reached

Potential Solutions:

• Ensure Sandbox services are running on each Full CRM 2011 Server.
  NOTE: Sandbox services are not required to be on a CRM Full serve role, but by using this option the local CRM platform and Async service will use the local sandbox instead of using one over the network.
• If you are hosting the sandbox service along with one of the IIS dependent server roles , ensure you have TCP port 808 listed within IIS manager bindings for net.tcp.

  Example: 
   
  Ref- For more port information: http://technet.microsoft.com/en-us/library/hh699823.aspx

• Check if you have the required SPN’s register against the Domain account used to run the Sandbox account. 
  NOTE: It is best practice to have least privileged account run the Sandbox service. 
  

Example: 
MSCRMsandboxservice/WebServerName 
MSCRMsandboxservice/WebServerName.Domain.com 
Ref- CRM 2011 security consideration article: http://technet.microsoft.com/en-us/library/hh699825 
Ref- Easy generation of SPN’s for CRM 2011 

If the issue is not still not resolved please open a support case with Microsoft for additional support.

Kaustubh Giri

Microsoft Premier Field Engineer