Hi @oppodeldoc
Actually update_sub_field does not have the ability to create new rows in a repeater or flexible field. It can only update existing sub fields
However I’ve posted a solution here which you should be able to use to figure this out: http://support.advancedcustomfields.com/forums/topic/create-new-repeater-row-from-front-end-form/
Good luck and let me know if that doesn’t do it for you 🙂
