This product is currently out of stock and unavailable

functions.php

Obviously this was frustrating, but after a little investigation, the fact that they were variations was the key to fixing the problem.

Typically WooCommerce allows 60 product variations in total when using ajax to update the variations on the product page, and in most cases the error message is due to the product exceeding this. Fortunately, there’s a relatively simple fix.

Add the following code to your functions.php file and you should be seeing your products back in stock in no time at all.

// Increase WooCommerce Variation Limit
  function custom_wc_ajax_variation_threshold( $qty, $product ) {
  return 100;
}

add_filter( 'woocommerce_ajax_variation_threshold', 'custom_wc_ajax_variation_threshold', 100, 2 );