Overview of the Issue
In Checkout Field Editor for WooCommerce, the custom fields you add to the contact, order and additional sections of the block checkout show their label, placeholder and options in the default language, even when you translate them in WPML String Translation.
Workaround
Until ThemeHigh fixes it, use the classic checkout, where the translated fields show:
- Go to Pages and edit the Checkout page.
- Select the Checkout block and click Switch to classic checkout.
- Translate the field labels, placeholders and options in WPMLString Translation, in the woo-checkout-field-editor-pro domain.