An agreement can have the status planned, active, negotiated, or closed. The planned status means that the agreement is being entered and will change to active whenever it is ready to be used. In order to create a customer schedule and run it through the schedule flow, the customer schedule agreement must be activated.
The customer schedule agreement has to be entered in order to receive status active.
If the agreement is changed to active, the agreement will be valid and you can create customer schedules for this particular agreement.