there are three points that cause the issue.
1) If the number of SAN attached to N8000 node is larger than 0, the issue will not appear. For file engine, the number of SAN must be 1, because file engine can only attach one SAN device. Or the issue will also appear.
2)please check if the hareware configuration of the new node is the same as the node of cluster, such as CPU and memory. If their configurations are different, the issue will appear.
3) If there is a new site, you also check the license file. If the node number of cluster that you install is 2, but the resource of all features is 1, less than 2, you will also fail to add node.
After we check the above points, we find the network between NAS and SAN is not correct. The new node can't find its SAN device. After adjust the network, we can add node.
If the above points can't help you to resolve the issue, please collect the /opt/HS/log/add_node_gw.log to check further.