Due to weird-ass PolicyKit rules, you may not be able to mount external drives – such as USB Hard drives, Pen drives, or other mass storage drives. while the drive gets recognised, on trying to mount you’ll end up with this error:
org.freedesktop.hal.storage.mount-removable no <– (action, result)
This is because of a PolicyKit rule, which prevents external media from being mounted. To get around this, you’ll have to edit the policy.