After configured the Let’s Encrypt in to Azure Webapp, SSL certificate request fail with “Lets Encrypt ACME server was probably unable to reach”

The problem is that Umbraco is takeover that path “~/.well-known/acme-challenge/…” and trying to route you to a document and failing to find one.

Fix: add new entries to the web.config file.

<system.webServer>
    ...
    <staticContent>
        <remove fileExtension="." />
        <mimeMap fileExtension="." mimeType="text/plain" />
        ...
    </staticContent>
    ...
</system.webServer>
...