index.php loading even with WooCommerce Declared

WooCommerce is being declared in my themes’ function file. However, I’m having an issue with the product pages’ loading index.php instead of the woocommere templates. I’ve isolated the problem to be happening at least when the SKU plugin is activated. Once deactivated and the permalinks flushed, the correct WooCommerce page template loads. Is anyone else having this issue? Any idea of how to fix? Thanks so much.