Test Case Parameters not present in Test Set and in execution

I'm experiencing an issue with using parameters in the test cases during the test case execution. I have identified e.g. two parameters in the test like ${login} and ${password}, however they are not shown in the Parameters section within the Test Set module.  When I press the 'EditParameters' or '+Add Parameter Value'  button I have a message either  'This test case does not have any parameters defined.' or 'There are no parameters you can add to this test set'.  Additionally, during the test case execution the parameters itself are not substituted with the defined values.  Would be grateful for any assist in this matter.