Hi Miguel1
I'm not sure if I understand how the SKU are automatically generated. They were added manually in your site or did you use a third party plugin to generate them?
Note when using ATUM, it takes the SKU data from Woocommerce, if you haven't set the SKU it won't be displayed in Stock Central.
Also, we give support in Spanish as well, so if you want you can change the language 🙂
Best Regards,
Andrea.