It sounds like Firefox has not played well with CAC readers without extra steps, although it is hard to tell what the current situation is. They all use proprietary drivers and software which may do unknown incompatible things. It also sound like many readers were never intended to be attached to a home computer in the first place and require a lot of effort to get up and running. Given that you know your model and software, you might have a look here. Most Firefox references are older, but it addresses Mac Catalina specifically. https://militarycac.com/ Maybe check out the "New" Mac Catalina reference, even if your device is not problematic. https://militarycac.com/MacVideos.htm#Firefox_6 You might even see the Windows references for configuring FF, using ActivClient, and importing certificates if those aren't covered directly for Mac. (All the Mac + Firefox stuff seems to be videos instead of web pages or PDFs.) https://support.mozilla.org/en-US/questions/752709 https://militarycac.com/files/Tech_Note_Firefox_CAC_Authentication.pdf