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.
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.