This article made something click for me.
If you impose economic sanctions on a country to encourage it to change its behaviour then you need to remove the sanctions if the target country meets your conditions. Moreover, leaders in the target country must believe you will remove the sanctions if they comply with your conditions. Otherwise, they have no incentive to change their behaviour.
The US seems to have a habit of imposing economic sanctions to merely express disapproval of a target country with no intention of ever removing the sanctions under some conditions. Such gratuitous sanctions will not change in behaviour. They do, however, work in the same sense that eating chocolate works to make you fell better.