We keep getting the error “No connection can be made because target machine actively refused it” when we try to use PMU Connection Tester to connect to one of our SEL-421 boxes. Based on another thread, we see possible errors being the IP address, Port #, or the Device ID. We are confident we have the right IP address and have IPV4 set to TRUE. We have tried standard ports 23 (telnet), 4712, and 4715 without luck. We are not sure if the Device ID matters. We have tried 235 (legacy), 0, 1, and 2, all without luck. We are able to connect to the box using SEL's acSELerator QuickSet program. We do not see anywhere in acSELerator what might be required for the Port or Device ID. We do not currently have an external clock driving the SEL-421 but are not sure if this matters for PMU Connection Tester. We also do not have the IP address for our network switch (we inherited it) but it does not seem to matter for acSELerator. Please provide any guidance for setting the Port or Device ID or what else could be causing the error. Thanks in advance!