LetsEncrypt 'Token did not match'

FreePBX Configuration
6

Probably your webserver redirects all HTTP requests to HTTPS.

Change the webserver config to restrict redirections:

<VirtualHost *:80>
 RewriteEngine on
 RewriteRule ^/(admin|ucp)/(.*)$ https://%{HTTP_HOST}%{REQUEST_URI} [NC,R=301,NE,L]
</VirtualHost>