Another user asked a similar question just last week:
Check to see if the accepted answer there solves your issue. If not, hopefully another user will chime in here to help you troubleshoot.
The following known issue has just come to light:
ADDON-8448 Splunk Add-on for Check Point OPSEC LEA does not support the 6.4 release of the Splunk platform. The add-on requires version 6.3.