After some update of the Operative System, my Mac will not mount any external drive (SD card, hard drive, micro-controller) automatically when I connect it to the USB port. I can see the device connected to the computer, but the device is not mounted, and the drive cannot be read nor you can write any file.

This is how I manually mount an external drive every time I need to use it.

Once the device is connected, list the local disks and volumes to see the path of the device you need to mount:

diskutil list

Create a directory where the device will be mounted:

sudo mkdir /Volumes/media

Mount the device; replace /dev/disk4s1 with the path of the disk you are trying to mount:

sudo mount -w -t msdos /dev/disk4s1 /Volumes/media