Hi,
Yes, quantity is disabled for open pricing products. However this is easily fixable. Please give me 1-2 days to release new version, where this will be optional. If you are in a hurry, you can temporary comment single line in “/includes/class-alg-wc-product-open-pricing-core.php” file in plugin’s folder. Just comment/remove line 29 there:
add_filter( 'woocommerce_is_sold_individually', array( $this, 'hide_quantity_input_field' ), PHP_INT_MAX, 2 );
Unfortunately I didn’t have time to test it, but this should be enough to re-enable the quantity field.
Will get back to you as soon as new version is released.
Best regards,
Tom