# The Certificate Authority failed to download the challenge files **URL:** \ **Category:** Help\ **Created:** [February 27, 2026, 3:07am UTC](https://community.letsencrypt.org/t/the-certificate-authority-failed-to-download-the-challenge-files/245574 "2026-02-27T03:07:26Z")\ **Posts on this page:** 5\ **Page:** 1
**Author:** ![cgyng49](https://avatars.discourse-cdn.com/v4/letter/c/c67d28/32.png) [@cgyng49](https://community.letsencrypt.org/u/cgyng49)\ **Post date:** [February 27, 2026, 3:07am UTC](https://community.letsencrypt.org/t/the-certificate-authority-failed-to-download-the-challenge-files/245574/1 "2026-02-27T03:07:26Z")
Please fill out the fields below so we can help you better. Note: you must provide your domain name to get help. Domain names for issued certificates are all made public in Certificate Transparency logs (e.g. [crt.sh | example.com](https://crt.sh/?q=example.com)), so withholding your domain name here does not increase secrecy, but only makes it harder for us to provide help. My domain is:cgyoung.ddns.net I ran this command: certbot certonly --standalone -v It produced this output: Saving debug log to C:\Certbot\log\letsencrypt.log Plugins selected: Authenticator standalone, Installer None Please enter the domain name(s) you would like on your certificate (comma and/or space separated) (Enter 'c' to cancel): [cgyoung.ddns.net](http://cgyoung.ddns.net) Requesting a certificate for [cgyoung.ddns.net](http://cgyoung.ddns.net) Performing the following challenges: http-01 challenge for [cgyoung.ddns.net](http://cgyoung.ddns.net) Waiting for verification... Challenge failed for domain [cgyoung.ddns.net](http://cgyoung.ddns.net) http-01 challenge for [cgyoung.ddns.net](http://cgyoung.ddns.net) Certbot failed to authenticate some domains (authenticator: standalone). The Certificate Authority reported these problems: Domain: [cgyoung.ddns.net](http://cgyoung.ddns.net) Type: connection Detail: 76.184.65.216: Fetching [http://cgyoung.ddns.net/.well-known/acme-challenge/kHUHqaWFrUbNcAog2swdKKZ923tXuZ4Wq6BBNMESA1k:](http://cgyoung.ddns.net/.well-known/acme-challenge/kHUHqaWFrUbNcAog2swdKKZ923tXuZ4Wq6BBNMESA1k:) Timeout during connect (likely firewall problem) Hint: The Certificate Authority failed to download the challenge files from the temporary standalone webserver started by Certbot on port 80. Ensure that the listed domains point to this machine and that it can accept inbound connections from the internet. Cleaning up challenges Some challenges have failed. My web server is (include version): Apache 2.4 The operating system my web server runs on is (include version): Windows 11 My hosting provider, if applicable, is:Netgear RS280 router connected to Spectrum modem 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):certbot 2.2.0 ---
**Author:** ![webprofusion](https://sea3.discourse-cdn.com/letsencrypt/user_avatar/community.letsencrypt.org/webprofusion/32/85310_2.png) [@webprofusion](https://community.letsencrypt.org/u/webprofusion)\ **Post date:** [February 27, 2026, 3:14am UTC](https://community.letsencrypt.org/t/the-certificate-authority-failed-to-download-the-challenge-files/245574/2 "2026-02-27T03:14:05Z")
> [@cgyng49](#): > > likely firewall problem It's likely a firewall (or your ISP) blocking TCP port 80 incoming. Certbot isn't supported on windows anymore btw, but that's not the cause of this issue. ---
**Author:** ![MikeMcQ](https://sea3.discourse-cdn.com/letsencrypt/user_avatar/community.letsencrypt.org/mikemcq/32/52772_2.png) [@MikeMcQ](https://community.letsencrypt.org/u/MikeMcQ)\ **Post date:** [February 27, 2026, 4:25am UTC](https://community.letsencrypt.org/t/the-certificate-authority-failed-to-download-the-challenge-files/245574/3 "2026-02-27T04:25:59Z")
Looks like you fixed your firewall / timeout problem. You really shouldn't be using Certbot on Windows anymore. Especially not for a new setup. And, if you insist you shouldn't be using --standalone method with Apache. The --standalone option needs exclusive use of port 80 but you have Apache using that port. Certbot usually won't issue a warning about this problem (on Windows). The cert request will just fail. You should switch to an ACME Client that supports Windows. See: [Certbot Discontinuing Windows Beta Support in 2024](https://community.letsencrypt.org/t/certbot-discontinuing-windows-beta-support-in-2024/208101) Good options for a stand-alone ACME Client are: Certify the Web (gui) [https://certifytheweb.com/](https://certifytheweb.com/) posh-acme (powershell) [Home - Posh-ACME](https://poshac.me/docs/latest/) simple-acme (command line) [https://simple-acme.com/](https://simple-acme.com/) Given you are using Apache another option is its `mod_md` feature. This is an ACME Client built-in to Apache. If you are reasonably skilled at Apache admin this might be the easiest. The Apache docs are a good reference and install overview: [mod\_md - Apache HTTP Server Version 2.4](https://httpd.apache.org/docs/2.4/mod/mod_md.html) The github for mod\_md has very good examples: [GitHub - icing/mod\_md: Let's Encrypt (ACME) in Apache httpd](https://github.com/icing/mod_md) ---
**Author:** ![cgyng49](https://avatars.discourse-cdn.com/v4/letter/c/c67d28/32.png) [@cgyng49](https://community.letsencrypt.org/u/cgyng49)\ **Post date:** [March 3, 2026, 3:03pm UTC](https://community.letsencrypt.org/t/the-certificate-authority-failed-to-download-the-challenge-files/245574/4 "2026-03-03T15:03:29Z")
Thanks MikeMcQ for all this nice information. I actually got CertBot to work by disabling my Firewall temporarily and got my Certificates created. I will look at certifytheweb when CertBot finally quits working when trying to renew the certificate. ---
**Author:** ![system](https://global.discourse-cdn.com/letsencrypt/original/3X/c/a/ca6c06ea1ea201324bba7048c6841ce60236468d.png) [@system](https://community.letsencrypt.org/u/system)\ **Post date:** [April 2, 2026, 3:04pm UTC](https://community.letsencrypt.org/t/the-certificate-authority-failed-to-download-the-challenge-files/245574/5 "2026-04-02T15:04:16Z")
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