Below are the NIC system error messages,

%NIC-3-500018: LSServer, LSServer, -, -, -, -, Detail: 832: Connection from NIC Server on Domain NIC, Site TRHSBC, Node TRHSBC-DS1 to NIC Server on Domain NIC, Site TRHSBC, Node TRHSBC-DS1 is Down - Failed to read nst file

%NIC-5-500017: LSServer, LSServer, -, -, -, -, Detail: 832: Connection from NIC Server on Domain NIC, Site TRHSBC, Node TRHSBC-DS1 to NIC Server on Domain NIC, Site TRHSBC, Node TRHSBC-DS1 is Up.

Solution
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Check the files in the below locations. I am specifying for ES. For LS, check for the same locations on NAS Vol0.

1. E:\nic\csd\config\<locators>\<node-name>\<node-name>.nst
2. E:\nic\csd\config\<collectors>\<node-name>\<node-name>.nst
3. E:\nic\csd\config\<nicservicemanagers>\<node-name>\<node-name>.nst

One of these or all files may be 0KB or corrupted.

Remove the specific file(take a backup) and restart NIC Service manager. This will resolve the issue and you won't see the above errors.