"No Cards" in Contacts
Running High Sierra 10.13.6 on a mid-2011 iMac. When I open Contacts the names of my contacts are all on the left side, but on the right side it says "No Cards." All my contacts show up in iCloud, on my iPhone, iPad and MacBook, but NOT on my iMac. They were there for years, but now they are gone. I have no idea what to do; looking for help.
iMac 21.5", macOS 10.13