In NSX-T 3.2.2.1 there is a condition within the NSX Manager which will cause the "search indexing" mechanism to report "Unknown" for certain Transport Nodes when queried.
NSX-T 3.2.2
This symptom can be caused by a stale Transport Zone issue OR an issue with the "search indexing" mechanisms.
This issue is resolved in NSX version 3.2.3.1.
If the above workaround does not work for you, please collect the below information and open a support request with Broadcom.
GET /api/v1/transportzone-profiles?include_system_owned=true
GET /api/v1/transport-nodes/
GET /api/v1/transport-nodes/<tn-uuid>