I've tried everything I can think of to get this resolved so if anybody is able to offer any new ideas of point me in the right direction, I'd really appreciate it. Essentially, my server just suddenly stopped working about a month ago. One day after a reboot, my domain was inaccessible from the web and upon trying to restart caddy to fix the issue I saw the "too many renewal attempts" error listed below. After doing some digging, I came across this: https://check-your-website.server-daten.de/?q=htpcomp.co.uk which suggests that port 80 is not available, but as I'm not aware of any changes to any of my setup, I'm struggling to determine if that is the cause of my issues, or a symptom.
if you want to use http validation, a working port 80 is required. See the explantation.
Fatal: Check of /.well-known/acme-challenge/random-filename is blocked, http connection error. Creating a Letsencrypt certificate via http-01 challenge can't work. You need a running webserver (http) and an open port 80. If it's a home server + ipv4, perhaps a correct port forwarding port 80 extern ⇒ working port intern is required. Port 80 / http can redirect to another domain port 80 or port 443, but not other ports. If it's a home server, perhaps your ISP blocks port 80. Then you may use the dns-01 challenge.
There is no working http port. Why? That's the problem you have to fix.