Some more information would be helpful (i.e. do you get error messages, or does client start, but then crash?).
Anyway, file a support ticket in order to get in line.
You can also try generic troubleshooting steps such as clearing the cache, and using revo uninstaller before reinstalling eve. And, depending on the issue, you might have luck telling the launcher to forget your accounts and then logging back in (this is something that I often have to do when I haven’t logged into the test server for a while).