Additional Information tab is displayed by woocommerce in case product weight or product dimesions are set to a non-zero value.
In case there is still need to display product addtional information tab then add the below code to your themes functions.php file.
add_filter(‘wc_product_enable_dimensions_display’,’show_addtional_info_tab_always’);
function show_addtional_info_tab_always(){
return true;
}
It generally needed when it requires to show some more info in additional info tab.