andiG

Problem:
Generally it is expected that a Custom Post Type Archive will not be accessible if no posts have been translated yet. In this case the client tried to create a custom language switcher to solve the issue.
Solution:
For custom language switchers, note that you can use the hook wpml_active_languages to manually generate the correct URLs for your language switcher. Here's an example, but take note that you need to adapt the code to your needs. For example "post-type-name" "slug-name" would be the slug that you would like to translate and this hook will make it translatable:

function force_cpt_archive_language_urls($post_type = 'post-type-name') {
    $languages = apply_filters( 'wpml_active_languages', NULL, array(
        'skip_missing' => 0
    ) );
 
    if ( !empty($languages) ) {
        foreach ($languages as $code => &$lang) {
            // Manually generate the archive link for the CPT in this language
            $translated_slug = apply_filters( 'wpml_translate_single_string', $post_type, 'slug-name', "URL slug: $post_type", $code );
            $lang['url'] = home_url( '/' . $code . '/' . $translated_slug . '/' );
        }
    }
 
    return $languages;
}

Please note, that this is a custom solution and might not have been tested in every setup. It's beyond WPML's built-in functionality, so our support doesn’t cover debugging custom code. If this solution does not resolve your issue or seems irrelevant due to being outdated or not applicable to your case, we highly recommend checking related known issues at https://wpml.org/known-issues/, verifying the version of the permanent fix, and confirming that you have installed the latest versions of themes and plugins. If further assistance is needed, please open a new support ticket.