PreOrder 3.9.8

- New feature: Added OpenCart 3.0.3.6 compatibility
- Bug fix: Preorder not back to out-of-stock when pre-order quantity 0

PreOrder 3.9.7

    - Improvement: Multi-store support
- Improvement: Use button name as default preorder note
- Bug fix: Default preorder text
- Bug fix: Default preorder quantity
- Bug fix: Preorder Note was hide when date is empty

https://digitalforest2.org/preorder-pre-order-out-of-stock-products