Hi All,
Hopefully someone can help out a noob 
Domain: matthewj.black
Command: /usr/bin/certbot certonly --dry-run --agree-tos --force-renewal --standalone --preferred-challenges http --http-01-port 54321 -d matthewj.black
Output: Saving debug log to /var/log/letsencrypt/letsencrypt.log
Starting new HTTPS connection (1): acme-staging.api.letsencrypt.org
Obtaining a new certificate
Performing the following challenges:
http-01 challenge for matthewj.black
Waiting for verification…
Cleaning up challenges
Failed authorization procedure. matthewj.black (http-01): urn:acme:error:unauthorized :: The client lacks sufficient authorization :: Invalid response from http://matthewj.black/.well-known/acme-challenge/CqJqXYPy7rdop5dcAsbe3HYeB-IEzwv1Usx_hBP18W8 [139.218.173.13]: 503
IMPORTANT NOTES:
-
The following errors were reported by the server:
Domain: matthewj.black
Type: unauthorized
Detail: Invalid response from
http://matthewj.black/.well-known/acme-challenge/CqJqXYPy7rdop5dcAsbe3HYeB-IEzwv1Usx_hBP18W8
[139.218.173.13]: 503
Server Centos7, HAProxy, Nginx
Self hosted web server, haproxy server; DNS hosted by NetRegistry (Australia)
The reported IP address is correct, the website is up and working AOK (both inside and out - via isup.me).
Any help would be greatly appreciated - thanks
Dulux-Oz