jQuery Grid Plugin - jqGrid

When grouping, is there something wrong with this code that cause all rows not to collapse? It 

looks good when I used the 1st column grouping but adding a 2nd column grouping showed the 

1st column as expanded row, with collapse icon, instead of collapse row.

var parmColumnName = 'Model';

$('#test').jqGrid('groupingGroupBy'), 
   parmColumnName, 
   {
       groupCollapse: true,
       groupField: ['name']
   }
);