Hi Jeffrey/Greg, Can you please try to upgrade the CAC Reader driver using details in link MilitaryCAC's Apple / OS X 10.11 (El Capitan) Resource page and let me know if issue is resolved/still reproducible? If you've just updated your Mac OS from 10.11.3 to 10.11.6 and your SCR 331, 3310, 3300v2, or 3500 model reader has stopped working, you may need to update the driver per https://forums.developer.apple.com/message/127598# You'll see in epeterso's 29 March reply where it has a link to the scmccid_mac_5.0.35.zip file Thanks, Shakti K
... View more