Did you try performing a factory reset? This procedure will restore the DNS-345 to the factory default settings, removing all user settings/shares/etc, but should not impact existing HDD configurations or data.
While the DNS-345 is powered up, press and hold the reset button on the rear of the unit for > 9 seconds.
FYI - you may want to remove your JBOD HDDs to avoid any potential data loss. Once the unit is restored, and assuming the JBOD was not damaged, you can drop the HDDs back in. This approach will afford you the opportunity to be more brazen in your recovery attempts without worrying about your data.