G’day kluchnyk,
An empty zip file suggests an error in the packaging process. If you can get hold of an error log, it should give some indication of what’s going wrong.
You can find your website error log through your hosting control panel, usually under a button called Logs. If you’re not sure where to find it, you can tell WordPress to write errors to the file wp-content/debug.log by editing your wp-config.php file. Find the line that says:
define('WP_DEBUG', false);
And replace it with this:
define('WP_DEBUG', true);
define('WP_DEBUG_LOG', true);
define('WP_DEBUG_DISPLAY', false);
NB: you should change it back when you’re finished, because debug mode slows your website down a bit!
cheers,
Ross