Your primary connection is against the system database and this is always reachable via 3xx13 (HANA 1.0) and 3xx15 (HANA 2.0) which isn’t, as far as i know, configurable and where xx is the instance number.
Can you run the plugin directly from the command line of the client?
MK_CONFDIR=/etc/check_mk/ /usr/lib/check_mk_agent/plugins/sap_hana --debug
(contains sensible information, don’t post ist without censoring it)
This could give you some hints whats may going wrong.