<?php

// save current language
$current_lang = apply_filters( 'wpml_current_language', null );

//get the default language
$default_lang = apply_filters( 'wpml_default_language', null );
//fetch posts in default language
do_action( 'wpml_switch_language', $default_lang);
//query args
$custom_query_args = array(
    'cat' => 1
);
//build query
$custom_query = new wp_query($custom_query_args);
//loop
while ( $custom_query->have_posts() ) : $custom_query->the_post();
    //check if a translation exist
    $t_post_id = apply_filters( 'wpml_object_id', $post->ID, 'post', false, $current_lang );
    if(!is_null($t_post_id)){
        $t_post = get_post( $t_post_id);
    ?>
        <a href="<?php echo get_permalink($t_post_id); ?>" title="<?php echo get_the_title($t_post_id); ?>"><?php echo get_the_title($t_post_id); ?></a>
        <?php
    }
    //no translation? display default language
    else{ ?>
        <a href="<?php the_permalink(); ?>" title="<?php the_title(); ?>"><?php the_title(); ?></a>
        <?php
    }  
endwhile;
wp_reset_query();
do_action( 'wpml_switch_language', $current_lang);

<?php
 global $sitepress;
// save current language
$current_lang = $sitepress->get_current_language();
//get the default language
$default_lang = $sitepress->get_default_language();
//fetch posts in default language
$sitepress->switch_lang($default_lang);
//query args
$custom_query_args = array(
    'cat' => 1
);
//build query
$custom_query = new wp_query($custom_query_args);
//loop
while ( $custom_query->have_posts() ) : $custom_query->the_post();
    //check if a translation exist
    $t_post_id = icl_object_id($post->ID, 'post', false, $current_lang);
    if(!is_null($t_post_id)){
        $t_post = get_post( $t_post_id);
    ?>
        <a href="<?php echo get_permalink($t_post_id); ?>" title="<?php echo get_the_title($t_post_id); ?>"><?php echo get_the_title($t_post_id); ?></a>
        <?php
    }
    //no translation? display default language
    else{ ?>
        <a href="<?php the_permalink(); ?>" title="<?php the_title(); ?>"><?php the_title(); ?></a>
        <?php
    }  
endwhile;
wp_reset_query();
$sitepress->switch_lang($current_lang);

shows list of cpt for example on archive page when wpml is installed. if particular post has no translation, it shows it in default language

wpml - show all CPT at archive page, default language if not translated

wordpress

PHP