with APM antivirus check in windows 8.1 vpn not working

Are you sure that its the antivirus thats the problem and not the detection of the OS ? There a few problems with windows 8.1 (https://support.f5.com/kb/en-us/solutions/public/14000/700/sol14781.html?sr=45825391) Try removing the antivirus scan and see if the client kan logon to the VPN, if they can then there is some problem with detection of the antivirus via opswat. Have you updated to the latest signature files:- epsec-1.0.0-393.011.5.0Patches05/14/2015OPSWAT Endpoint Security Integration SDK 3.6.9993.2 Update That could help.

/Craig