I am trying to create a mount point in /mnt like the example below in linux Mint 18.

sudo mkdir /mnt/myMount

Which results in a message saying it can not be done because the file system is read-only (?)
Another computer with the exact same Linux mint executes the command with no problem.
also, when I try to see what is in it using sudo ls /mnt I get the message can access lost/found input/output fault.

Listing the permissions of the directory with ls -l results in:

drwxr-xr-x 3 root root 4096 sep 7 23:17 mnt

What am I doing wrong?