Hi
this sounds that your current (trial?) license has expired. If so you must decide if you are willing to by real enterprise or switch to free license. Here you could see the difference of licenses: Types of Splunk software licenses .
If you want to go free you (probably) can do it this way: https://community.splunk.com/t5/Getting-Data-In/Heavy-Forwarder-change-trial-license-to-forwarder-li... just change Forwarder to Free on previous example.
If you still want to keep enterprise you must buy valid license from Splunk and install it there. Other option (you lost you data and configs) is just remove installation and install that trial again.
r. Ismo
