Why is there an error when I try to run a custom report with the product revenue metric?

The Product Revenue metric requires that the Product Quantity metric be included in the report as well. This is a limitation due to the fact that there are price and quantity columns in the log_conversion_item table, but not a revenue column.

So, the report needs to calculate the revenue by multiplying price with quantity and the revenue metric can only be tied to one of those columns automatically. As part of the next major release of Matomo, the revenue column may be added to remove the current limitation.