Side note:
$ nmap -Pn -p80,81,443 atavismxi.com
Starting Nmap 7.94SVN ( https://nmap.org ) at 2023-12-27 19:58 PST
Nmap scan report for atavismxi.com (98.25.54.173)
Host is up (0.11s latency).
rDNS record for 98.25.54.173: 098-025-054-173.res.spectrum.com
PORT STATE SERVICE
80/tcp open http
81/tcp filtered hosts2-ns
443/tcp open https
Nmap done: 1 IP address (1 host up) scanned in 1.92 seconds
Best Practice - Keep Port 80 Open
The HTTP-01 challenge can only be done on port 80. Allowing clients to specify arbitrary ports would make the challenge less secure, and so it is not allowed by the ACME standard.