How do I release preorder orders that are on hold? (Essent Preorder Back in Stock app)

If your campaign's fulfilment status is On hold, Shopify holds the preorder items until you release them.

In Shopify, go to Orders and open the order.
In the fulfilment section marked On hold, click Release hold. Shopify may warn about an app's fulfilment agreement. It's safe to continue.
Fulfil as normal.

Good to know

Shopify only lets you release holds one order at a time. There's no bulk release button in Shopify or the app. To automate it, use the Shopify Flow action Release preorder fulfilment hold.
Filter preorder orders in Shopify by the tag Essential Preorder (or your own campaign tag).
Scheduled orders release themselves on the due date (around midday store time).
New stock arriving doesn't release existing orders automatically.
On hold and Scheduled need Shopify Payments.