Strange problem - automatic PK generation doesnt work (Apex)

Hi all,

first of all i want to apologize for the meaningless title but i cant describe it better in a few words.

I haven't really developed since Apex 3.x and now want to build a small application, unfortunately I have a strange problem that I can't explain to myself. Probably it's totally self-explanatory and I just don't see the solution.

I read, that i dont have to bother with sequence and triggers anymore for PK, so i created the PK column like this:

"C_ID" NUMBER GENERATED BY DEFAULT AS IDENTITY MINVALUE 1 MAXVALUE 9999999999999999999999999999 INCREMENT BY 1 START WITH 1 CACHE 20 NOORDER  NOCYCLE  NOKEEP  NOT NULL ENABLE