Outdoor camera shows base with no SD card

I have two Outdoor camera setups at two homes. There are SD cards in the cameras and the base stations, and the cameras were set to backup to base. Some of the cameras show “No SD card” under Base Station MicroSD card, and others on the same base show the size of the SD card. What’s up with that. If I go back later, it may now show the size of the SD card.