Похоже, что вам не хватает имени владельца последовательности.
Пример (который на самом деле работает ).
SQL> show user
USER is "SCOTT"
SQL>
SQL> create sequence seq;
Sequence created.
SQL> grant select on seq to hr;
Grant succeeded.
SQL> connect hr/hr
Connected.
SQL>
SQL> select scott.seq.nextval from dual; --> owner.sequence name.nextval
NEXTVAL
----------
1
SQL>
Синоним:
SQL> connect hr/hr
Connected.
SQL> create synonym seq for scott.seq;
Synonym created.
SQL> select seq.nextval from dual;
NEXTVAL
----------
2
SQL>
Публичный синоним:
SQL> connect scott/tiger
Connected.
SQL> create public synonym seq for seq;
Synonym created.
SQL> connect hr/hr
Connected.
SQL> select seq.nextval from dual;
NEXTVAL
----------
3
SQL>