I agree with Tom Mc's recommendation. You do need to upgrade your Universal Server to Symantec Encryption Server version 3.3.0 to deploy new Symantec Encryption Desktop 10.3.0 clients.
There are ways around this by updating your server with the Desktop client only PUP file (usually only around 350-400 MB download instead of the larger PUP update). But this is not a recommended solution for optimal performance since the server usually works better working with a current branch version.