There is a condition that the Orders from Subscription cannot be created because it is linked to an unavailable gift, even if the items of a subscription are available.

• To simulate this, you need a gift (like Promotion Buy One Get One) linked to one SKU of subscription, and this gift should be unavailable after the purchase is made and before the next cycle.
• The error on the subscription cycle is "Could not select a SLA for SKU {SKU ID}"

The way to avoid this scenario is to remove the link of gift out of stock or guarantee that the gift has stock if you want to create a new cycle with the gift.