Make sure that you can login to the database with the SQL Management Studio using SQL authentication and the sa account. Once you're logged into the instance, make sure you don't have the SEEMSdb listed. (If it only partially created during installation you'll need to remove it before installing again.) Also make sure that the database account you attempted to create during installation is not listed under Securtiy > Logins. If its there and you attempt installation again, you'll get a 27506 error. If its there delete it or specify a different account during install. After checking these things, try the installation again, only this time enable logging for the installation. Paste this into run.
MSIEXEC /i "[path]\Symantec Endpoint Encryption Management Server.msi" /lvx [logpath]\logfile.log
Look through the log for value 3 if the installation fails.