Follow the below mentioned Instruction's :
1. Check whether NI XNET Driver's are Installed on the PXI RT target and compatible with the system, to check compatibility do refer the Read me file NI XNET as per version installed on system, for example : NI-XNET 18.0 Readme
2. Do verify the NI XNET Card is being detected properly under Remote System in NI MAX as shown below :
3. The name of XNET Interface port (CAN1 or CAN2) should be same as seen in NI MAX in system definition file of NI VeriStand.
4. Follow this tutorial Getting Started with NI-XNET for NI VeriStand and NI LabVIEW
for configuring the system definition file of VeriStand project
For more information on XNET Database refer Related Link's section