One of our users gets an HTTP 500 error when he tries to run a business process from his LF client, but not from the workflow designer. 

We have checked his workflow configuration console and successfully tested his connection. The client machine is able to ping the server by name and IP without issue. The Web application directory URL is valid and we can see all the HTTP methods and routing.

It seems like all systems are go but for whatever reason he's still getting a server error. Any ideas?

Error Code: 0
Error Message: Error launching Business Process:
     Entry: [entry removed by poster]
     Error Type: Network Error
     Error Message: The remote server returned an error: (500) Internal Server Error.

------------ Technical Details: ------------

LF.exe (10.4.1.147):
     Call Stack: (Current)
         LaunchBusinessProcess
     Call History:
          CGroupProvider::raw_GetAllGroupIdentifiers
          CGroupProvider::raw_GetAllGroupIdentifiers
          CGroupProvider::raw_GetAllGroupIdentifiers
          CGroupProvider::raw_GetAllGroupIdentifiers
          CGroupProvider::raw_GetAllGroupIdentifiers
          CGroupProvider::raw_GetAllGroupIdentifiers
          CGroupProvider::raw_GetAllGroupIdentifiers
          CBusinessProcessManager::GetStartingInstructionsDocument