Important note: 
With the Windows security update of May 2018, access to HTML help in the local intranet is permanently blocked, so that the following solutions suggested by Microsoft no longer work.
Access is now possible again by updating the CONVAL Client installation to version 10.4.1. For older CONVAL versions we are not aware of any workaround at the moment.

The issue with the CONVAL help system might be caused by a Microsoft security update.

Excerpt from the Microsoft webpage:

“Certain Web sites and HTML Help features may not work after you install security update 896358 or security update 890175

SYMPTOMS

After you install security update 896358 or security update 890175, you may experience one or more of the following symptoms:

• Certain kinds of Web-based programs may not work correctly. For example, a table of contents in HTML Help may no longer work.
• Certain HTML Help features may not work when you open a .chm file from a remote location. For example, the Related Topics feature may not work.“

See http://support.microsoft.com/kb/892675 for more information.

In the download section of our homepage you find a registry patch, which allows the access to HTML files in the local intranet.