Hello
Can you tell us a bit more about your deployment? Were you using El Capitan and then upgraded to Sierra, or is this a new Sierra install? It may be likely that the reader you have needs a new driver to support MacOS 10.12.
Does the Smartcard display in the keychain? Have the necessary certs been added?
A good place to start is this thread, "[Read Me 1st] – Common OS X Smart Card troubleshooting steps" which links to the milirary provided site to help with general Smartcard issues, including updating your driver.
I hope this helps!
Have a great day!
Ryan V.