Verify FQDN property (used by transport nodes to talk with NSX Manager or controller) is set by running API: GET /api/v1/configs/management and view value for publish_fqdns.
If FQDN is set, verify the controller FQDN is reachable and FQDN value is being used to by the transport node to talk to controller by first running ICMP ping to controller FQDN followed by admin cli
get controllers to verify controller FQDN value is getting populated correctly.