If you are using an operating system from RedHat family: Before installing Parallels Plesk Panel, switch SELinux off by running command 'setenforce 0' in shell. After you have installed Parallels Plesk Panel, switch SELinux on by running command 'setenforce 1'
You can find more information about this in the following article:
Could you please also check (or paste here) /var/log/sw-cp-server/error_log file, also try to restart Plesk CP manually with
/etc/init.d/sw-cp-server restart
and let us know the error you are getting
It appears that stale pidfile of 'sw-cp-server' is the problem. Just try to stop 'sw-cp-server' service and remove /var/run/sw-cp-server.pid
Then re-run installation to continue.