Message d'erreur lors d'une demande de renouvellement de certificat Let's Encrypt, voici le message et la solution plus bas :

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Demande d'un certificat pour machintruc.ltd, www.machintruc.ltd à Let's Encrypt ..
.. la demande a échoué : La validation basée sur le Web a échoué : Échec de la demande de certificat :

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 149, in get_crt
raise ValueError("Challenge did not pass for {0}: {1}".format(domain, authorization))
ValueError: Challenge did not pass for www.machintruc.ltd: {'identifier': {'type': 'dns', 'value': 'machintruc.ltd'}, 'status': 'invalid', 'expires': '2020-08-17T22:05:29Z', 'challenges': [{'type': 'http-01', 'status': 'invalid', 'error': {'type': 'urn:ietf:params:acme:error:unauthorized', 'detail': 'Invalid response from http://www.machintruc.ltd/.well-known/acme-challenge/bUBuWqUw4i2dVVxvynyoz8b9xXXxlLu1AJyxxXxx-Zz [IP.xx.xx.xx]: "\\n\\n403 Forbidden\\n\\n

Forbidden

\\n<p"', 'status':="" 403},="" 'url':="" '<a="" href="https://acme-v02.api.letsencrypt.org/acme/chall-v3/6444719401/5D-91g'">https://acme-v02.api.letsencrypt.org/acme/chall-v3/6444719401/5D-91g', 'token': 'bUBuWqUw4i2dVVxvynyoz8b9xXXxlLu1AJyxxXxx-Zz', 'validationRecord': [{'url': 'http://www.machintruc.ltd/.well-known/acme-challenge/bUBuWqUw4i2dVVxvynyoz8b9xXXxlLu1AJyxxXxx-Zz', 'hostname': 'www.machintruc.ltd', 'port': '80', 'addressesResolved': ['IP.xx.xx.xx'], 'addressUsed': 'IP.xx.xx.xx'}]}]}

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SOLUTION :

C'est simple et basique :
autoriser l'accès au dossier ".well-known" et aux sous dossiers.