Simple Product detail page “Add to Cart” not adding to cart

Mostly writing to report a flaw in the way simple product detail pages are submitting their Add to Cart form.

In the latest version of Woocommerce, Simple Product detail pages submit their add-to-cart product id value through a <button> element. Unfortunately this doesn’t work consistently and should likely be rewritten as using a hidden <input> element with name=”add-to-cart”. This was how we solved the issue.

Unfortunately we’ll have to continuously apply this fix whenever Woocommerce plugin gets updated, but here’s what we do to fix:

Open /plugins/woocommerce/templates/single-product/add-to-cart/simple.php

Add:
<input type="hidden" name="add-to-cart" value="<?php echo esc_attr( $product->get_id() ); ?>">

Comment out the <button> submit and replace it with an input submit:
<input type="submit" value="<?php echo esc_html( $product->single_add_to_cart_text() ); ?>" class="single_add_to_cart_button button alt">

Hopefully Woocommerce can apply this fix for future updates. Using a <button> submit with values attached doesn’t work as expected.