This is likely due to the way that Splunk changed the SSL key-value pairs in version 6.5.0. Did you update your local server.conf and ssl.conf configurations with the new SSL stanzas?
sslRootCAPath =
* Full path to the operating system's root CA (Certificate Authority)
certificate store.
* The must refer to a PEM format file containing one or more root CA
certificates concatenated together.
* Required for Common Criteria.
* NOTE: Splunk plans to submit Splunk Enterprise for Common Criteria
evaluation. Splunk does not support using the product in Common
Criteria mode until it has been certified by NIAP. See the "Securing
Splunk Enterprise" manual for information on the status of Common
Criteria certification.
* This setting is not used on Windows.
* Default is unset.'
caCertFile =
'* DEPRECATED; use 'sslRootCAPath' instead.
* Used only if 'sslRootCAPath' is unset.
* File name (relative to 'caPath') of the CA (Certificate Authority)
certificate PEM format file containing one or more certificates concatenated
together.
* Default is cacert.pem.'
