Check these 2 might work..
Please take a backup of the registry before proceeding further.
- Open Regisrty Editor
- Browse to HKEY_USERS\.DEFAULT\Software\Microsoft\Windows\CurrentVersion\Explorer\User Shell Folders
- Select the Expandable String Value 'AppData' and change the value to : %USERPROFILE%\AppData\Roaming
- Close the registry editor
- Delete folders for Sep if found under c:\program files\
- C:\prgramdata\
- or C:\users
- Reboot the computer
- Install SEP client again.
Secondly
Please confirm if you are able to install SEP 12.1 unmanaged with only "Virus and Spyware Protection".
If we are able to install SEP with basic protection then we can try below steps to install SEP with all features installed.
1) Create a Test Group
2) Edit Application and Device control policy for Test Group.
3) Click on Application Control.
4) Uncheck the option "Protect client files and registry keys" .
5) Create a new package so that the clients report to the Test Group.
6) Use the package for installation .
Please Check if the installation works.