Symptoms

When trying to update the Plesk license key via web interface the following error is shown:

*Unable to connect to license server https://ka.plesk.com:5224/xmlrpc.
cURL error description: Problem with the SSL CA cert (path? access rights?)(77)*

Cause

System packages nss-softokn, nss-softokn-freebl updates for CentOS 6/CentOS 7/RedHat EL6 installed on Plesk server.

Resolution

Connect to the server via SSH and restart sw-engine:

# service sw-engine restart