Regular price not showing

Hi, I’ve installed this plug-in to allow me to show ‘Call for price’ against one variation product. It works correctly for this product (with no price) by showing ‘Call for price’ and removing the ‘Add to cart’ button. However, for other variation products it is also removing the price. It now just shows stock, quantity box and ‘Add to cart’ for the other variation products. Is this a bug or is there a setting I need to set? If I deactivate the plugin, all products show the price before the stock level. Thanks