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. 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.
It produced this output: There was an error updating the certificate: HTTP Challenge for s-reeves-webrtc.forge-cloud.com is not available. Whole response: {“type”:“urn:acme:error:unauthorized”,“detail”:“No registration exists matching provided key”,“status”:403}
My web server is (include version): Apache 2.2
The operating system my web server runs on is (include version): Centos 7
My hosting provider, if applicable, is: N/A
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): FreePBX 13
I'm afraid this is an inaccurate conclusion. There's no issue related to finding registrations by key on the Let's Encrypt side. This would be a result of a bug with the ACME client that FreePBX is using. Hopefully @bytecamp is correct that it has since been fixed upstream by the FreePBX developers.