When any of you restart PLESK from TELNET using the following command:
/usr/local/psa/rc.d/psa restart
Make sure you stay logged in about 30 seconds to a minute *after* the command has *fully completed*. Failure to do so will stop *ALL* HTTPS (SSL) services / sites, including access to the PLESK control panel which is on HTTPS port 8443 by default.