$(#).css not working

$(#).css not working

It  appears that the script code does not fire for some reason. Any ideas?
css
.isvisible {
   visibility : visible
}
.notvisible
{
   visibility : hidden
}
 
Html (works)
< div id ="SectionLink" class =" notvisible">
   @Html.Partial( "Partial/_SectionDisplay" , Model)
</ div >
 
<script>
$(document).ready(
function () {
  $(
'#P1').change(function () {
    $("#SectionLink").css("isvisible"); (Does not work)
  });
});
</script>