SPE link to self-service not working, getting "service not available" error.

Hello,

SPE has been installed on our Windows 7 computers, and the self-service URL has been configured in the administration console - General Settings - Realm Instances.

When users click the "Forgot My Password" link on the Windows password change screen, the self-service URL does not come up; they get a "service not available" error. However, they ARE able to access the self-service URL when they manually enter the URL into their browsers. What could be causing this to happen?

Thank you in advance for any guidance.