It sounds like you also need to set the classpath in your nsd.tcl file. Something like the following:
ns_section "ns/server/${server}/module/nsjava"
ns_param EnableJava "on" ;# Set to on to enable nsjava.
ns_param VerboseJvm "off" ;# Same as command line -debug.
ns_param LogLevel "Notice"
ns_param DestroyJvm "off" ;# Destroy jvm on shutdown.
ns_param DisableJITCompiler "off"
ns_param ClassPath "/usr/local/jdk/jdk118_v1/lib/classes.zip:/home/nsadmin/bin/nsjava.jar:/home/nsadmin/bin/activation.jar:/home/nsadmin/bin/mail.jar:/home/nsadmin/mirror/acs3-pg/www/webmail/java"