Check if your boot folder is empty using
cd /boot/ in a terminal session. If so, you should be able to mount it to the SD card using a simple command.
sudo mount /dev/mmcblk0p1 /boot
All this command does is mount the boot partition on your SD card. Which explains the
The boot partition is not mounted - cannot configure. error.
sudo raspi-config looks for the
config.txt which is located on the boot partition. If the boot partition isn't mounted,
raspi-config will not be able to find your
config.txt file. Thus, no configurations can be made.
That should do the trick. However, if that doesn't work then there's another problem. Good luck, tell me any other information about this problem if it comes up.