The reson for that issue is we don't have permissions to preview it.
To fix it follow below steps.
- Go to IIS-->Local Host-->Sites
- Click on PPS Monitoring
- Right click on Preview and click Edit Permissions.
- Then you will get the Preview Properties. Click on the Security tab and click on the Edit button.
- Then add the current user by allowing Full Control.
- After that that click Ok and you will be able to preview the dashboard...