- Plesk Onyx
Docker loses the connection when Plesk Firewall was installed or rules were modified.
Firewall rules related to docker are missing in FORWARD chain:
# iptables -v -S FORWARD | grep docker
This is Plesk bug with ID #PPPM-7924 that is planned to be fixed in future Plesk updates.
As a temporal workaround restart Docker in Home > Tools & Settings > Services Management.