PDF Invoices not getting translated when attached to emails

[alexmigf]

A customer reported issues with translating PDF attachments when using WPML.

I am using the free version of this plugin (3.9.3), together with WPML, and it has been working wonderfully for years! Our default site language is not English, and invoices were always correctly sent in our default language.

However, after upgrading WordPress to version 6.7 (known to have caused several issues with localization) and persisting through 6.7.1, invoices attached in emails (!) are not translated to the default site language, but are all in English. The issue does not happen when previewing invoice directly in WordPress.

I believe this is due to Main.php:139, where translation is being unloaded, then load_plugin_textdomain is called for the second time, which has no effect anymore and the translations are not reloaded.

I have been able to fix this issue by putting

add_filter('wpo_wcpdf_allow_reload_attachment_translations', '__return_false');

into our theme’s functions.php file.

I hope this solution helps anyone else having a similar problem.