The GUI runs under the current user while the service that does the real work runs as local system. If you’re doing something like setting a PATH variable with your OpenSSL path, it won’t be available to the service. You can just put a cd to your OpenSSL path before calling OpenSSL and that should work.
As for what you can pull from the passed variable in PowerShell, I made a list(might be old?) here: List of Script Variables
I would try $result.ManagedItem.Name for what you called the entry and $result.ManagedItem.DomainOptions.Domain for the domain name?