First off, serial devices aren't SkyView Network devices, so you won't see them there. All their setup troubleshooting is done on the serial port setup.
The lack of RX counts indicates that the RX line isn't hooked up. Is the transponder getting independent ship's power? I'd start by looking at the complete wiring of the transponder.
Same thing here. Under the serial port setup, do you have the right serial port set to the SV-GPS-250? Any RX counts / good sentences? Is the GPS puck getting power?
For both of those devices, do you have all the serial wires (and the power/ground for the GPS puck) paralleled off to both displays' serial ports if you have more than one display? And do you have the serial ports configured on each display individually?
You might give our tech support a call at 425-402-0433 when you're at the airplane for more personal help here.