v8 upgrade problem w/ Elasticsearch

I am trying to upgrade 7.9.4 to 8.0.1 SugarPro.

Sugar 8.0.1 supports, and requires, an Elasticsearch upgrade.

Based on this:

http://support.sugarcrm.com/Resources/Supported_Platforms/Sugar_8.0.x_Supported_Platforms/ 

We went with ES 6.2.1 for Sugar 8.0.1

Sysadmin set up a new VM for me with Elasticsearch 6.2.1 following instructions here:

http://support.sugarcrm.com/Knowledge_Base/Installation_Upgrade/Installing_and_Administering_Elasticsearch/#ES_Configura… 

When I attempt to point 7.9.4 to the new VM with ES 6.2.1 I get the following errors:

   

Tue Nov  6 14:12:45 2018 [9177][2053ed63-d2dc-52e8-0049-4ddab9fc33f1][FATAL] Elasticsearch: connection went away to elasticsearch-tst.mycompany.com:9200

Tue Nov  6 14:12:45 2018 [9177][2053ed63-d2dc-52e8-0049-4ddab9fc33f1][FATAL] Elasticsearch verify conn: failure

Tue Nov  6 14:12:45 2018 [9177][2053ed63-d2dc-52e8-0049-4ddab9fc33f1][FATAL] Elasticsearch no longer available

 

We verified that the sugar application server can see the ES server.

 

Now, I understand that 7.9.4 is not compatible with ES 6.2.1 but following the upgrade instructions it is recommended to point Sugar to a new, upgraded ES before upgrading to v8 and reindex - which is what I'm trying to do.. 

 

The errors seem to come from:

/var/www/html/sugarcrm/src/Elasticsearch/Adapter/Client.php

public function verifyConnectivity

and

public function onConnectionFailure

Now that same script has 

protected $allowedVersions = [
   '1.4',
   '1.7',
];

 

So, how do I get 7.9.4 to see ES 6.2.1?

What are my sysadmin and I missing?

 

thanks,

FrancescaS