You cannot make an assignment to make-to-order stock

Hi

At production order creation for a variant configuration sales order, error message CO684 "You cannot make an assignment to make-to-order stock" is coming out. The planning strategy is 25, tried with 20 also but with the same error. I can see there have been a few discussion already but I still cannot find out what's wrong. Settlement rule is SD1 and production order type is PP01.

Thanks for any input

milk