If you find that any of your product pages display an error saying %NaN instead of the price.
You simply need to resync the products by going to the Ruleset at the top and hit Save.
For one-time products, this usually happens when a duplicate product is made on Shopify that was originally copied from a subscription product. If you just add the product to a subscription ruleset, save, then remove it, that will clear out the issue on the product page.
If you try following these steps and it doesn't work for any reason, contact us to help you resolve it.