When sd card is not detected by the camera/baby monitor, you can do the followings:
If the sd card is too hot, you can cool it down and then run the camera later.
1. Take out the sd card and then install another one to test if it is the problem of this sd card.
2. Take out the sd card and then format it on pc and install it again to the camera.
3. Upgrade the camera and the app to the latest version.
If the problem still exists after the above 3 ways, it might be the damage of the sd card slot inside the camera. Contact seller for further solution.