Invalid response 404 with win-acme and IIS

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My domain

I ran this command: I tried installing SSL on my IIS webserver and it produced the output below. My IIS webserver is on a local IP address and a public IP address is port forwarded to the local IP address

It produced this output: [] {"type":"urn:ietf:params:acme:error:unauthorized","detail":" Invalid response from 404","status":403,"instance":null}

My web server is (include version): IIS

The operating system my web server runs on is (include version): windows

My hosting provider, if applicable, is:

I can login to a root shell on my machine (yes or no, or I don't know): yes

I'm using a control panel to manage my site (no, or provide the name and version of the control panel): no

The version of my client is (e.g. output of certbot --version or certbot-auto --version if you're using Certbot): win-acme

Hello @mevicluv, welcome to the Let's Encrypt community. :slightly_smiling_face:

Side note: Port 443 is Closed.

$ nmap -Pn -p80,443
Starting Nmap 7.80 ( ) at 2023-06-23 22:28 UTC
Nmap scan report for (
Host is up (0.27s latency).

80/tcp  open   http
443/tcp closed https

Nmap done: 1 IP address (1 host up) scanned in 0.77 seconds

Edit: I also see this with curl -i (3.5 KB)


Make sure your win-acme is using the self-hosting option for http challenges (which temporarily sits in front of IIS on port 80 and catches the challenge requests), otherwise your IIS (Web Application) needs to be configured to serve the challenge response files.

Also make sure port 80 is being forwarded to this server and not some other one.


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