Trouble installing Let's Encrypt SSL

I am having trouble installing the Let’s Encrypt SSLs on my server.

I have pointed the domain name to the correct ip address, and this shows correctly on dnschecker.org.

The server is on my LAN, and I have forwarded port 80 and 443 to the server’s internal ip address.

When I try to issue Let’s Encrypt SSL, there seems to be an authentication error and a self-signed certificate gets issued instead.

I seem to have the same problem with a VPS which is not on the LAN.

I am using Ubuntu 22.04 with the latest version of Cyberpanel (v.2.3). I am hosting my DNS records with bunny.net.

I have watched a number of videos and tried to make sure that I am following the procedure correctly, but nothing I do seems to make a difference. I have also tried SSL v.2 on the paid subscription, but that doesn’t help either.

Any help will be greatly appreciated!