Depending on how your WooCommerce system is set up, adding product variations can take a long time to process. This can also cause some product variations to fail to transfer to your store. This is an external WooCommerce issue that Printbest does not have control over.
We recommend contacting WooCommerce or WordPress for technical help to increase your memory limit and maximum execution time on the WordPress system. If you notice that some variants were not transferred successfully to your store, we recommend checking your WooCommerce error log.