Hello,
I assume you mean Windows Server 2008 R2?
Symantec Endpoint Protection 14.3 RU5 is supported on 2008 R2.
14.3 RU6 only support 64-bit
https://knowledge.broadcom.com/external/article/163625/windows-compatibility-with-symantec-endp.html
For Windows 2008 RTM is 14.2 MP1 the latest supported version.