SystemCleaner agent does the delete of expired passivated requestors data. As per the code, passivated requestor context data is deleted it is older than 2 days. It can controlled by the below DSS setting.
PassivationDaemon has to be running in order to passivate the idle requestors (and then SystemCleaner will delete the expired passivated requestor data). Take a look at the PegaRULES log files to see if there is any reason that PassivationDaemon may have been stopped.
You will need to bounce the JVM in order to restart PassivationDaemon.