Dashboard Map - Timed Refresh won't occur

I have a Dashboard Map I am working on, I am creating a custom object to display the time in Hours : Minutes and have the dashboard set to refresh every 60 seconds so to keep the time up to date.

The issue I am having is the Dashboard will never refresh, though as soon as it is loaded it constantly shows the buffering/loading symbol on my browser.

Code for the Custom System Time:

function renderTime(offset) {

  var currentTime = new Date();
  currentTime.setHours(currentTime.getHours() + offset);
  var diem = "AM";
  var h = currentTime.getHours();
  var m = currentTime.getMinutes();

//Defines AM/PM over 24 hour
  if (h == 0) {
    h = 12;
  } else if (h == 12){
    diem = "PM";
  } else if (h > 12, h < 24) {
    h = h - 12;
    diem = "PM";
  } 

//Adds a 0 in front of single digit hours
  if (h < 10) {
    h = "0" + h;
  }

//Adds a 0 in front of single digit minutes
  if (m < 10) {
    m = "0" + m;
  }

//Output
  var myClock = document.getElementById("clockDisplay");
  myClock.textContent = h + ":" + m + " " + diem;

//Return tag to get values in PRTG - if omit, h and m will show as NaN
  return;
}
  renderTime(+0).valueOf();

Note: I don't recall this issue happening before I started using this custom object, does JavaScript cause issues with Dashboards?

custom-object dashboard maps prtg