Hi Adi,
The access sequence 0004 uses source com_partner_b to do the determination.
You need to make sure the user that you want to be determined is a central person.
That means, the user should be assigned to a BP that is created in BP role bup003 (employee) or bup005 (internet user).
Can you please check, is the user a central person?
Or you can debug the partner determination, the form to do the determination with source com_partner_b is get_partner_by_uname (LCOM_PARTNER_OWF15).
Best regards,
Maggie