Using the online tool Let's Debug yields these results https://letsdebug.net/sesstim4.timone.univ-amu.fr/1676006
ANotWorking
ERROR
sesstim4.timone.univ-amu.fr has an A (IPv4) record (139.124.158.220) but a request to this address over port 80 did not succeed. Your web server must have at least one working IPv4 or IPv6 address.
Get "http://sesstim4.timone.univ-amu.fr/.well-known/acme-challenge/letsdebug-test": read tcp 172.104.24.29:36006->139.124.158.220:80: read: connection reset by peer
Trace:
@0ms: Making a request to http://sesstim4.timone.univ-amu.fr/.well-known/acme-challenge/letsdebug-test (using initial IP 139.124.158.220)
@0ms: Dialing 139.124.158.220
@1198ms: Experienced error: read tcp 172.104.24.29:36006->139.124.158.220:80: read: connection reset by peer
IssueFromLetsEncrypt
ERROR
A test authorization for sesstim4.timone.univ-amu.fr to the Let's Encrypt staging service has revealed issues that may prevent any certificate for this domain being issued.
139.124.158.220: Fetching http://sesstim4.timone.univ-amu.fr/.well-known/acme-challenge/UUOPrMZMnLilOvDrVIoVP8svITn_-hAhe87Q9xIdQqg: Connection reset by peer
Do per chance have a Palo Alto Firewall?
$ curl -Ii http://sesstim4.timone.univ-amu.fr/.well-known/acme-challenge/sometestfile
HTTP/1.1 404 Not Found
Date: Wed, 15 Nov 2023 03:12:09 GMT
Server: Apache/2.4.52 (Ubuntu)
Content-Type: text/html; charset=iso-8859-1
$ curl -Ii http://sesstim4.timone.univ-amu.fr/.well-known/acme-challenge/sometestfile -A "Mozilla/5.0 (compatible; Let's Encrypt validation server; +https://www.letsencrypt.org)"
curl: (56) Recv failure: Connection reset by peer