When I add a Subscription Item to a Sales Order (CRONUS environment - V27.2)

I get the following error:

“The Subscription does not exist. Identification fields and values: No.=''

I have created an item 1001 – for Business Central licenses, and it is Non-Inventory and set to “Subscription Item” – there is one Subscription Line created (I have a 12M Subscription Package assigned to the Item): 

When I go to Post (Ship & Invoice) I get the error I mentioned at the beginning of my email. The system should automatically create a Subscription Line No. using the No. Series that I have set up in the Subscription Contract Setup, but it does not.