Initially, you might have thought that you can add 50 variations to products in WooCommerce. This is not true, you certainly can have way more variations than that. The important part is “max 50 per run” (by default, you can add only 50 at a time) – what this means
You may experience this issue after upgrading to WooCommerce (ver. 2.0+), purchased order using PayPal payment never get complete, in fact, all purchased order status goes to “Cancelled” and in the admin area those orders showed up as cancelled with the message “Unpaid order cancelled – time limit reached”. This