This rule already exists
An hourly rate already exists for this customer/project/service/employee
Check the list of hourly rates for any existing hourly rates associated with a data record. If you have a large number of hourly rates, you can use the keyboard shortcut "CTRL+F" / "CMD + F" to search within the page.
You can then either delete the hourly rate and create a new one, or simply edit it.
You can then either delete the hourly rate and create a new one, or simply edit it.