Defect in the 8.1 RU3 Servicedesk Installer. A file is missing to allow the page to render properly.
This only affects the rendering of the page in the SMP portal, and the ability to download the Servicedesk installer link from this page. A later release will address the issue. The actual Servicedesk installer can be obtained from the SMP by using the following path in a browser to download the msi:
You will need to change the <SMP_Base_URL> to match the name of your SMP server.