Thanks!
Currenly Chrome is the only browser working with Centrify Express on MacOS. Safari was working a couple weeks ago, but seems to be tempormental now. I don't believe Firefox was ever supported?
With Chrome, if I completely quit Chrome and start fresh, when I try to authenticate to a website, Chrome will first ask me which certificate I want to use, then prompt for my PIN. Closing the logged in tab, then opening a new tab and navigating back to the same website works. As long as I don't remove my smartcard. Once I remove my smartcard, I can no longer authenticate to any website. I must completely quit Chrome and start over.
This behavior is specific to Centrify Express with the CACNG driver. I didn't experience this with the default OS X CAC driver.
Thanks again for the assistance!