CFexpress card reader not being recognized

You might be looking in the wrong place. CFExpress cards are seen as removable disks by Windows and MacOS, so this card will not show in the usual 'Connected Devices', but among any other external drives. That means you may have to click 'Browse' (assuming this is the same on Windows, this screenshot is from a Mac).

...  I have no problem with UHS-11 card readers but CFexpress does not come up on my "add photos". 

...

By @Jay5EF2

Do you seen the card reader in Windows Explorer?

Confused, your other card reader, a different format, allows you to Add in import?

Trying to Add in import should be blocked on either reader usage. 

'You can use the Add option when the photos are on a hard drive, you cannot when they are on a card.

This is by design.

/edit/followup/ Ohhh, my error, clearly Lr not LrC. So the above not exactly correct.

You want to post in the Lightroom (Ecosystem) forum. You have posted in the Lightroom Classic forum, but your question is not about Lightroom Classic.