By default some browsers will block pop-ups unless you tell them otherwise. And this is normally a good thing. But sometimes it’s hard to tell that they are blocking content that may be perfectly legitimate.
In Google Chrome, when you click on the new “Login to hosting control panel” button in the clients site nothing may happen at first, but if you look closely you will see that your browser is displaying a small notification in the top right corner.
If you click on the notification icon you will get a dialog box where you can tell your browser to allow popups for this site.