This is due to the changes that Apple has brought in. The following link details regarding Catalina specific changes for smartcard - HT210541
Apple has changed the existing framework and mandated to use cryptotokenkit framework instead of TokenD which was used until Mojave release. The driver support to read certificates from smart card is provided by third party packages. However with Catalina, these are broken as none of the software providers are supporting it.
Of the two flavors of smart card – PIV based and CAC based, Apple has very recently provided drivers for PIV based smart card. Pulse Secure is working on supporting the same on priority and will update the KB once we have an ETA on the release which will have the support.
However so far none of the third party software's currently support CAC based smart card on Catalina. We are constantly monitoring the developments in open source community and will incorporate changes to our code to support CAC based smart cards as and when its available.