Plesk license key says invalid and can't update

[abubin]

I am using old plesk 8.1 version but my plesk suddenly give error "You can try to update it later. The key cannot be upgraded due to the network failure during connection with the Key Authority server. Please check that your Internet connection is configured, you can resolve and access ka.swsoft.com and your firewall enables outgoing connections to TCP port 5224."

I have checked TCP port 5224 is working. And that the DB keys is not corrupt as said in some sites but that is linux related. This is windows. The only thing I did between that is restore my windows from a backup version done few days earliar. Please help.