I don’t know Trane tracer so keep that in mind. Typically the LAN is single pair shielded cable cable looped from VAV to VAV. The end of the run VAV may need a termination resistor. The home run goes from VAV controller to first VAV box. Each VAV box needs a unique address. There is usually a limit on total wire length and number of VAV’s.
How I would proceed would depend on if it is new and never worked versus a problem that just developed.
It can be labor intensive. You might have to disconnect LAN from all VAV’s and starting from VAV 1 reconnect each one verifying each VAV thermostat and CFM from disconnected linkage, manually manipulated, matches expected box number.
If it used to work than usually you will see valid information up to a certain box number. Disconnect at that point and work forward until things go haywire. Usual suspects are someone didn’t set proper address or you have a bad board on a box.
On your computer interface check to make sure you have sequence of numbers with no missing ones and, especially no two boxes with same address. Sometimes guys move a VAV controller from non critical area when one fails without knowing they need to set address and hose system.
