CORS issues with request filtering

Symptoms:

  • The UI portal does not load.

  • Network traces in the browser's developer tools indicate failed preflight requests. The following image shows the Network tab in Chrome's Developer tools view (keyboard shortcut in Chrome, Edge, and Firefox browsers: F12 or Ctrl+Shift+I).

    The locaton of the Network tab in Chrome's Developer tools view.

Possible causes:

The OPTIONS verb is disallowed in the IIS Request Filtering control.

The OPTIONS verb is disallowed in the IIS Request Filtering control.

Resolution:

Allow all HTTP Verbs (especially OPTIONS) in the IIS Request Filtering control by setting them to True in the Allowed column.