CAC reader has stopped working on my MAC

Welcome Marti68,

Have you tried to unplug the CAC reader from the MacBook Air, then restart the Mac (using the Apple menu > Restart), then reconnect the CAC reader again? If not, we'd suggest doing so now to test it out. These simple steps may resolve issues similar to this.

Should it persist, do you have any other cables or devices you could test on that Mac's USB or port? Does the port work properly on the MacBook Air? Any changes when you attempt testing this in safe mode: How to use safe mode on your Mac - Apple Support

Let us know and we'll continue to help out, cheers.

I'm afraid I can't provide any more insight than destiny241 already did, but the definitive place for CAC reader support is:

https://militarycac.com/macnotes.htm