Hi
Welcome to Centrify community!
The reason you are seeing the issue is because you are configured to use User certificate to authenticate the Radius Server which requires users to actually login to to the machine in order to see the certificate.
To wrokaround this issue, you can choose to use Machine Certificate to authenticate the Radius Server instead, which make the machine to have Wifi connection even if it's at the login windows and does not require user to login.
Here is an KB article that covers the steps on the configuration:
KB-2798: How to setup a workstation authentication certificate for autoenrollment or Mac OS X
Hope it helps. Thank you!
BR
Ivan