By Justin Doughty
Something I noticed on my own Revit 2018 Installation was that when the help icon was pressed, it took you to a URL that was not found. I simply worked around this by changing the last letter of the URL to U, to read ENU.
However, to permanently fix this, go to:
C:\Users\**YOUR USERNAME**\AppData\Roaming\Autodesk\Revit\Autodesk Revit 2018
Then find the Revit.ini file:
Open the Revit.ini File with Notepad or similar, and add the following line to the [Documentation] Section:
OnlineHelpLocale=ENU
Now Restart Revit, click on the help icon and it should direct you to the correct online help page.
For more information on this refer to the Autodesk article below: