Hi Igor,  It looks like you could be running into a variation of this:  498573 : Unable to register Isilon cluster as Ambari host: Agent for zone could not connect to its Ambari server [URL]   
Hi,  My env: OneFS: 8.1.0.1 Ambari: 2.5.2 HDP: 2.6.2  I'm using this guide [URL] page 27.   I'm creating a cluster and it fails when I try to add my SmartConnect  zone to it.  The message is not informative at all: "Registering with the server... Registration with the server failed."  The Isilon log file shows a bit more information. But as far as I understand it just means it times out while trying to connect to Ambari Server: /var/log/hdfs.log ... 2018-02-12T01:41:43Z <30.4> its-isiwlg-p01-2 hdfs[5816]: [hdfs] Ambari: Agent for zone 4 could not connect to its Ambari server. Agent will attempt to connect again later. 2018-02-12T01:42:43Z <30.4> its-isiwlg-p01-2 hdfs[5816]: [hdfs] Ambari: Agent for zone 4 could not connect to its Ambari server. Agent will attempt to connect again later. 2018-02-12T01:43:43Z <30.4> its-isiwlg-p01-2 hdfs[5816]: [hdfs] Ambari: Agent for zone 4 could not connect to its Ambari server. Agent will attempt to connect again later. ... so, nothing more informative, at least to me, either.   Do you have any idea what it may relate to? And what are the next steps to troubleshoot it.   Regards, Igor Gorbatovsky. 
Isilon SmartConnect zone adding on "Cluster configuration" step fails.