That is simple.   As documented in the install memo, LISTSERV needs
access to the disk containing BITEARN NODES, XMAILER NAMES, and DOMAIN NAMES.
 
I would check LISTSERV's PROFILE EXEC to make sure that the disk is
accessed.   You might want to logon as LISTSERV and enter
CMS Q SEARCH
 
to have LISTSERV reveal what it is currently accessed to.