I cannot send group messages in Contacts anymore from my Mac Mini

[S&W627shooter]

Does anyone know how to fix a problem in the Contacts app?  I used to be able to send group emails by typing the name of the group like ICORE 1 in the BCC line of the email, but those groups I created do not show up when I type ICORE 1 in the BCC line.  It still works on my iPhone, but not on my Mac Mini.  When I open contacts and click on the group ICORE 1, I can see all the names, but in the window on the right where it normally shows all the contact info for each contact I select, it says "no Cards"

I'm confused

Chris