Exception retrieving custom activity info using SandboxPlugin

Issue

Upon importing a solution containing a Sandbox plugin assembly, or registering an assembly in Sandbox mode, the following error is thrown:

Exception retrieving custom activity info using SandboxPlugin – Unhandled exception: Exception type: Microsoft.Crm.CrmException Message: Unable to retrieve customActivityInfo using RetrieveCustomActivityInfoWithSandboxPlugin. at Microsoft.Crm.Workflow.ObjectModel.CustomActivityInfoMetadataBase .GetCustomActivityInfo(ActivityInfo activityInfo, Int32 isolationMode, Guid pluginAssemblyId) — End stack trace —

Investigation

Registering in ‘none’ mode works fine.

Sandbox assembly registration takes too long and fails with the above message. In addition, a buried Windows event log entry indicated that the Sandbox service cannot communicate with other server nodes.

Checking communication between the frontend and backend (hosting the Sandbox service) servers indicated a network block. One of the following quick tests could be used to check for a block:

1. Telnet
   1. Telnet must be enabled/allowed on the server
   2. Open a command line from inside the frontend server
   3. Enter the following: telnet <backend-ip-address> 808
   4. Notice the space between the IP address and the port
2. TCP Ping: here
   1. Try to ping the backend IP address and port 808 from the frontend server

Solution

Remove or resolve whatever is causing the blocked connection.

Possible causes:

1. Windows firewall on either servers
2. Security software firewall on either server
3. Network switch rule between the servers
4. The Sandbox service itself stops for some reason