Unable to connect to basic functionality in Portal for ArcGIS

Description

Deploying a base deployment and other ArcGIS Enterprise add-ons may result in issues with basic functionality, including (but not limited to):

• Connecting to a portal via a web adaptor in ArcGIS Pro.
• Unable to bring services into ArcGIS Pro.
• Unable to configure Geo Enrichment Services.
• Fonts and/or icons do not load within Portal for ArcGIS.

Using Fiddler to debug the web application returns the following error message:

Error: 
HTTP Error 404.7 - Not Found. The request filtering module is configured to deny the file extension.

File extension filter settings are found within Internet Information Services (IIS) Manager.

Cause

Portal for ArcGIS and its underlying processes use many custom file extensions. Access to these file extensions is limited when the 'Allow unlisted file name extensions', 'Allow unlisted verbs', and 'Allow high-bit characters' options are disabled in the Request Filtering section of IIS Manager. Group policy dictates the enabled/disabled settings in IIS Manager, and they may be disabled for security purposes.

Solution or Workaround

Follow the steps below to resolve the issue:

1. Launch IIS Manager.
2. Select the active web server.
3. Select Request Filtering in the IIS sub-section.

4. Click Edit Feature Settings... to open the Edit Request Filtering Settings dialog box. Check the Allow unlisted file name extensions, Allow unlisted verbs, and Allow high-bit characters check boxes.