Check the following:

Sphere will only allow a certain amount of pop-up windows to be open at once. If other Sphere pop-up windows are open, close them and click on the link again.

The fully supported browsers for using Sphere on the back end are Internet Explorer version 7 and version 8 in a PC Operating System (or used through a PC Emulator on a Mac Operating System). If you are using a different browser or operating system that could be why the window isn't opening. Switch to either Internet Explorer 7 or Internet Explorer 8 on a PC system or used through a PC emulator on a Mac system.

If this does not resolve the issue, Chat with Support and reference this article.