Sales price already defined in conditions

What causes this issue?

In creation mode you selected the option specifying that prices can
only be calculated for items which do not yet have a sales price.
However, a sales price already exists for the current item.

System Response

No sales price was calculated for the current item.

How to fix this error?

If you want to change the existing sales price or want to create a new
sales price for an additional unit of measure, remove the relevant
indicator on the selection screen in creation mode or use the change
mode in Sales Price Calculation.

Error message extract from SAP system. Copyright SAP SE.