How to click on drop down with on-toggle property

  <div ng-if="domainList.length>1" class="form-group ng-scope">
            <div class="col-sm-3">
                <label translate="ZillaMain.Authentication" class="ng-scope">Authentication</label>
            </div>
            <div class="col-sm-9">
                <label uib-dropdown="" keyboard-nav="true" on-toggle="toggled(open)" class="dropdown">
                    <a href="" tabindex="0" aria-label="" uib-dropdown-toggle="" class="dropdown-toggle" aria-haspopup="true" aria-expanded="false">
                        <!-- ngIf: authentication_domain -->
                        <!-- ngIf: !authentication_domain --><h3 ng-if="!authentication_domain" class="ng-scope">
                            <span translate="ZillaMain.Select" class="ng-scope">Select</span>
                            <i class="icon angle-down-icon"></i>
                        </h3><!-- end ngIf: !authentication_domain -->
                    </a>
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With the above mentioned code I am trying to clcik on the dropdown:

this.AuthDD = element(by.css('[on-toggle="toggled(open)"]'));

AuthDD.click();

But this does not click on the drop down and My test does not fail also... I am not sure what is wrong with it.

I have also tried changing the locator by: element(by.css('a.dropdown-toggle')); or element(by.css('[translate="ZillaMain.Select"]')); but it does not clcik on the dropdown.

Is there any different way available in protractor to click on a dropdown ?