Error using Start Process Link in an Interface

Hi,

I am trying to use startProcessLink in a grid view Interface so that an user can edit the selected record by selecting a location Name. This is my first time using this method. 

When I am selecting an entry, I am getting an error message:

 An Error Has Occurred No process parameter found corresponding to override [name=pv!locationId]. Non-parameter process variables cannot be overridden.

a!gridColumn(
        label: "Location Name",
        sortField: "description",
        value: a!linkField(
          links: {
            a!startProcessLink(
              label: fv!row.description,
              processModel: cons!BC_PM_ADD_LOCATION,
              processParameters: { locationId: fv!row.locationId }
            )
          }
        ),

My process model is working fine. So how and where do I fix it? 

Please advice me. 

Thanks