The problem lies in a mismatch of the name used to identify the exit on the Find callable service/service.
In TestServer, the Find callable service the exit is called Exit, whereas on the Find service in TestClient it is called Exit 2. As you may have noticed, exit names beginning with the string 'Exit' are hidden (the same applies to triggers starting with 'Trigger'). To see hidden names select the slot (trigger/exit) and check the role property, or open the Rename dialog.
Obviously, what you need to do is to make sure the same name is specified in both services, since they are used to match parameters and results sent between the tiers.
In the future I suggest you explicitly name all slots on a callable service (even if there's only one) to avoid this annoyance.
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