If a product was delivered directly from an external supplier but the dish is showing as a missing cost price, you will need to add the product to a self managed supplier in order for the dish to update. The price in the dish will not update if you have amended the price in Selling and cost prices. You will need to create the product via Products & Categories and then link it to the supplier. Follow the steps below:
Click on Products & Categories.
Click on Purchaser Products.
Click on Add Product.
Enter the details of the product.
Once created click into the product.
Complete all details.
To link to the supplier this can be done form the Buy From tab.
Select from the drop down listing and enter the price.