If Symantec Endpoint Protection Manager (SEPM) included SEP 12.1 RU5 is installed by user who has "C:\Windows\Temp" for TEMP/TMP environment variables, "C:\Windows\Temp" folder's permission is changed during SEPM installation.
As the result, SEPM console doesn't appear.

"C:\Windows\Temp" has all non-inherited permissions. By installation of SEPM RU5, these settings has removed.

Workarounds

A. Install by another administrative user who has default TEMP/TMP variables. 

B. Enbale temporary folders for sessions available while installing SEPM to make sure installer will not change ACLs of C:\Windows\Temp.

1) Go to following location in registry

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Terminal Server

and set following keys' values: 
  fDenyTSConnections : set to 0. 
  fSingleSessionPerUser: set to 1. 
 PerSessionTempDir: set to 1.

2) Log-Off from machine and re-login.

3) Go to following location in registry

HKEY_CURRENT_USER\Volatile Environment\1 or HKEY_CURRENT_USER\Volatile
Environment\2 or HKEY_CURRENT_USER\Volatile Environment\3

and make sure following keys are present 

TEMP 
TMP

4) Start Installing SEPM.