Price Calculations plugin not working on product page

Hi,

The calculated price is usually displayed after a user selects / enters something in a custom item field. In your case, you're using the plugin without any custom item field, which is unconventional and not something the plugin was made for in the first place.

If you want to have an automatic markup on prices, you don't need this plugin. Create a custom product field of the type "text" via the menu Display>Custom fields in order to store the price of the products before the markup. Then, create a mass action (menu System>Mass actions) with triggers after a product is created / updated, and an action "update the values" on the price_value column, with the "operation" mode and the value "{product.xxx}*1.2" where xxx is the column name of your custom product field.
Then, in each product, you can configure the original price in your custom product field (near the end of the product edit form) and when you'll save, the mass action will auto fill the product price with the markup. It will work everywhere: listing, product page, cart, checkout, etc.