This is a solution for a problem with mounting some SD cards on linux.
You got an Unable to access… error or Error mounting /dev/sdcX at /media/user/mount_point: unknown filesystem type ‘exfat’ when you plug-in a SD-card. The same error may occur when you try to mount exfat filesystem manually.
Some SD Cards and USB sticks are formatted with extfat. The problem occurs because exfat-fuse package is missing in your operation system.
Install required packages exfat-fuse and exfat-utils.
sudo apt-get install exfat-fuse exfat-utils