Hi,
this setup works only in case there's at least one agent in Available state in the Skill Group(s) specified in the Skill Group node. In other cases, routing will continue at the Failure exit of the Select node.
Of course, even with this setup, if the system finds an agent in Available state, the agent will get that call, and if the agent misses it, it will count as a RONA call and the system most likely will switch the agent state to Not Ready.
Call errors are a bit different, for instance, ICM is able to see the agent as available, instructs CUCM to send the call to the agent's phone, but the call never arrives (for example, due to missing Device Target - which indicates a configuration issue -, or network related problems or simply because the agent became busy in the meantime).
Can you be perhaps more specific on what "Error" column are you looking at?
G.