- Plesk Onyx for Linux
80 port if filtered:
# nmap -p 80 example.com
PORT STATE SERVICE
80/tcp filtered http
Error during Let's encrypt certificate installation either on the domain, e.g
example.com, or on Plesk:
PLESK_ERROR: Detail: Fetching http://alias-plesksupporttest.tk/.well-known/acme-challenge/do75fK79n_uF9JimlezVpQQQfmvHaOVd7T8cjZKVvWk: Timeout during connect (likely firewall problem)
The domain example.com is hosted on the same Plesk server, and only IPv4 address is assigned to it.
Port 80 is filtered by a firewall.
If the firewall is configured on the Plesk server, open the port 80 for incoming connections as described in the article Which Ports Need To Be Opened for all Plesk Services to Work with a Firewall?
If some intermediate firewall/router is configured between the Plesk server and an external network, port 80 should be opened on it as well.