RVI Will Not Work Via Thinnet (Coax). It works fine with UTP (Cat 5).
Make sure you are using 50 Ohm BNC cable, not 75 Ohm. 75 Ohm BNC is for video signals and will not function properly for Thinnet.
Also make sure you are using T's and 50 Ohm terminators correctly. Only one terminator should be grounded, and that one should be at the console. T's have been known to fail easily, so if in doubt use a continuity meter to check them or replace them, as they are fairly inexpensive. DIP switches must be set at the console and the RVI. The DIP switch at the console will be labeled in reverse of how the switch should be. Use the DIP switch settings in the manual to set this correctly.
Make sure that the remote devices are powered up before the console. The console needs to seek out other devices on line during boot-up.
Make sure that both units are running the same version of software. If unsure, locate the software version that the console is running, find the Remote Units Disk that is the same software version. Run the Remotes Units Disk and update RVI. After the transfer is complete, cycle the power on the console, then cycle the power on the RVI.
Try setting the RVI closer to the console. Sometimes shortening the cable run will let you upload the code better. This will also eliminate problems with your other ethernet connections.
You may need to cycle power several times for them to talk to each other.
Use a different RVI to make sure the problem is not the console.