You can not change ownership on a read only filesystem. The mount
command will list if the partition is mounted read only. Probably not the problem since you say it does not complain (as it would if it was read-only).
But you can also NOT change ownership on a filesystem that is NOT posix (that includes all Windows filesystems). Changing ownership on Windows filesystems is done when mounting the partition.
If this is the case add "uid=1000,gid=1000" to the line in /etc/fstab related to this mount. 1000 is the main user; if you want another check the userid with id -u {user}
and the groupid with id -g {user}
.