In which schema, did u create the trigger?
use the before delete trigger and not AFTER trigger.
i tried all the alternatives but it didn't work. when i tested deleting a line not from the panneau forms in the EBS but with delete from it works. I doubt that the problem is from the panneau form
Not sure if a trigger is a good idea, but anyway, I'd suggest you to check what is the situation in the record right before it's deleted by INVTOTRX. I.e. create another trigger like
CREATE TABLE xxxx_log(text VARCHAR2(4000));
CREATE TRIGGER AFTER DELETE ...
INSERT INTO xxxx_log(text) VALUES (:old.organization_id || ' ' ||:old.transaction_type_id || ' ' ||:old.move_order_line_id);
And check if the values there are what you expect. Maybe INVTOTRX is changing something in the row before it deletes it.