Placeholder Translation is not working

[mohitkadelongraph]

I added attribute placeholder="{{ 'LANDING.WRITE_MSG' | translate }}" in

<ng-simditor content="vm.contactEmailModel.message" name="message" 
ng-model="vm.contactEmailModel.message" 
placeholder="{{ 'LANDING.WRITE_MSG' | translate }}" 
class="full-width" ng-model-options="{ updateOn: 'blur' }"  maxlength="1023">
</ng-simditor>

which is printing {{ 'LANDING.WRITE_MSG' | translate }} as a placehoder

angular: 1.6
angular-translate: 2.14.0