Please check the mount options of /dev/sdb3 in /etc/fstab.
man mount:
defaults
Use the default options: rw, suid, dev, exec, auto, nouser, and async.
Note that the real set of all default mount options depends on the kernel and filesystem type. See the
beginning of this section for more details.
nouser
Forbid an ordinary user to mount the filesystem. This is the default; it does not imply any other options.
users
Allow any user to mount and to unmount the filesystem, even when some other ordinary user mounted it. This
option implies the options noexec, nosuid, and nodev (unless overridden by subsequent options, as in the option
line users,exec,dev,suid).