Spark Workgroup chat (though fastpath) Issue on cross forest

Dear Team,

We had two open fire server in different forest. Version 3.7.1 and another one server 3.6.3. We had installed Fast path service on both server and working fine on both server seperatly. And we are using spark for chatting. But when we try to add fastpath workgroups which is available on server1 and try to chat from server2 its not working. Can you pls help whether this will work or any configuration needs to be enable on both server level.

Appriciate your help on this.

Thank You

Krishna