It's weird. That's working perfectly for us.
Are you using the latest versions of WordPress, WooCommerce and ATUM?
If so, it could be some other plugin conflicting with ATUM. If you are able to do so, go to your plugins page and disable all your 3rd party plugins except WooCommerce and ATUM and try again. If it works in that way, you can start enabling them one by one until you find which is causing this.
Also, you could take a look at your PHP error log. Perhaps you have there some error regarding this.