It means the PARENT does not exist. Looks like you're trying to add an entry BEFORE adding the entry corresponding to the suffix of your database.
I thought that at first, but the PARENT is without
a doubt in the database. Evidence:
$ ldapmodify -D <ROOTDN> -f modifications.ldif
$ ldapmodify -D <OTHERDN> -f modifications.ldif
The first succeeds and the second fails with "No such object".