Nouveau VPS et Let's Encrypt : certificate verify failed (_ssl.c:661)

Bonjour,

J'installe régulièrement des VPS, encore un le mois dernier sans problème, que je gère via Virtualmin.
Mais aujourd'hui, je rencontre un souci pour installer un certificat SSL de Let's Encrypt sur le dernier.
Ma config : VPS 2020 Starter, Debian 9.
Voici le message que j’obtiens et que je ne comprends pas.

Traceback (most recent call last):
File "/usr/share/webmin/webmin/acme_tiny.py", line 198, in
main(sys.argv[1:])
File "/usr/share/webmin/webmin/acme_tiny.py", line 194, in main
signed_crt = get_crt(args.account_key, args.csr, args.acme_dir, log=LOGGER, CA=args.ca, disable_check=args.disable_check, directory_url=args.directory_url, contact=args.contact)
File "/usr/share/webmin/webmin/acme_tiny.py", line 143, in get_crt
raise ValueError("Wrote file to {0}, but couldn't download {1}: {2}".format(wellknown_path, wellknown_url, e))
ValueError: Wrote file to /home/xyz/public_html/.well-known/acme-challenge/tqSYmVRwHm0ShlcX_26OK8oOzMvwnzC3GSwn4yUDVZA, but couldn't download http://xyz/.well-known/acme-challenge/tqSYmVRwHm0ShlcX_26OK8oOzMvwnzC3GSwn4yUDVZA: Error:
Url: http://xyz.fr/.well-known/acme-challenge/tqSYmVRwHm0ShlcX_26OK8oOzMvwnzC3GSwn4yUDVZA
Data: None
Response Code: None
Response:


Merci pour votre aide.