Using the TwitchCLI the result is
$ twitch event verify-subscription cheer -F https://dev.clickitfame.com/twitch/webhook/callback
✗ Invalid response. Received <!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0//EN">
<html><head>
<title>401 Unauthorized</title>
</head><body>
<h1>Unauthorized</h1>
<p>This server could not verify that you
are authorized to access the document
requested. Either you supplied the wrong
credentials (e.g., bad password), or your
browser doesn't understand how to supply
the credentials required.</p>
<p>Additionally, a 401 Unauthorized
error was encountered while trying to use an ErrorDocument to handle the request.</p>
</body></html>
as body, expected 3aa60148-3314-44b5-27f7-3d644ebf6c9d
✗ Invalid content-type header. Received type text/html with charset iso-8859-1. Expecting text/plain.
✗ Invalid status code. Received 401, expected a 2XX status
Your server cannot be reached due to the basic authentication dialog