Hello,
SEP 12.1 RU1 MP1 does not support Windows 8 machines.
Check this Similar query - https://www-secure.symantec.com/connect/forums/symantec-endpoint-protection-121-ru1-mp1-windows-8-compatibility
Windows 8 is supported in SEP 12.1 RU2.
The Release is due by November 6th. Check this -
http://www.symantec.com/business/support/index?page=releasedetails&key=54619
Secondly, Check this Article:
About Windows 8 and Symantec Endpoint Protection 12.1
http://www.symantec.com/business/support/index?page=content&id=TECH174348
Incase, if you are interested in Beta Testing for SEP 12.1 RU2, check this :
https://symbeta.symantec.com/callout/?callid=1D5D3DD349C248E69B13977DA4DBF426
In order to be considered for this program you must be registered with Symbeta. If you are already registered, log in with your username and password. If you have not yet registered, you will need to create a Symbeta account and provide the necessary information.
Hope that helps!!