Get element by id not working

Hello All,

I am trying to show a pop up and its not working. Due to upgrade to latest vbcs version.

Please see my vbcs function below:

  PageModule.prototype.showtestpopup = function () {  

     document.getElementById('rollbackPopUp').open();

     return null;

  };

And here my ui code

<oj-dialog style="display:none" dialog-title="Confirmation Alert" id="rollbackPopUp">

  <div slot="body">

    <div class="oj-flex">Rollback Payroll</div>

  </div>

  <div slot="footer">

    <oj-button on-oj-action="[[$listeners.ojButtonOjAction6]]">Ok</oj-button>

    <oj-button on-oj-action="[[$listeners.ojButtonOjAction7]]">Cancel</oj-button>

  </div>

</oj-dialog>

Kindly advise.

Thanks,

Mitish