WooCommerce “Sale!” sticker has disappeared!

Hi,

Now this is a strange one… out of nowhere, the Sale stickers, which automatically appear over the top of products on Sale, has disappeared.
What’s interesting about this, is I have copied the “sale-flash.php” file to our theme directory and amended it (see example: https://code.tutsplus.com/articles/customize-the-behavior-of-the-woocommerce-sale-flash–cms-22225)

This has restored the beloved banner in the category pages, but oddly, on the homepage and on the single product page itself, it is missing! It is also missing on products that are out of stock.

I can’t seem to find anything relative to it’s behaviour or this very random bug.

Has anyone come across this before? Does anyone have any suggestions on where to explore next?

Many thanks in advance!