Juniper is currently not Windows 8.1 compatible.
When will Juniper Network's SSL VPN platforms and UAC platforms support Windows 8.1 (codenamed Windows Blue) Internet Explorer 11 (IE11) as a supported client to connect to SA and MAG SSL VPN platforms?
Juniper Networks is in the final stages of qualification process and releasing software that supports Windows 8.1 and IE11 (schedule as listed below) In the interim if you are experiencing an issue with the features that are going to be supported and if the issue is not listed below then please report it to Juniper by opening a support case