Official Response from ACF.
As for custom fields on orders, with Woo’s introduction of HPOS, they’ve moved order data, and order metadata to dedicated tables. This means ACF isn’t able to read or write the data required for posts to work. They’ve also changed the internal post type for orders which breaks location rules. We’re currently assessing the best way to bring support for HPOS in Woo to ACF.
For now, if you go to WooCommerce settings > Advanced > Features, you can enable compatibility mode and once it has synched your orders back to the legacy format, you can then toggle “WordPress posts storage” as the storage mode, which uses the legacy post names and tables to store your data which is compatible with ACF.
