QNAP NAS Error Code 40: How to Fix It

Easy 15-30 minutes Medium Severity Verified June 2026
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Error Code
40
Brand
QNAP
Product Type
nas
Severity
Medium
DIY Difficulty
Easy
Estimated Fix Time
15-30 minutes
Error code 40 on your QNAP NAS indicates an iSCSI initiator timeout, meaning the connection between the NAS and the iSCSI target has been lost or is unresponsive. This usually happens due to network issues, misconfigured iSCSI settings, or target overload. Follow these steps to restore iSCSI connectivity.
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Tools You'll Need

How to Fix Error Code 40

  1. Check Network Connectivity

    Do not unplug cables while data is being transferred to avoid corruption.

  2. Restart iSCSI Service on QNAP

  3. Verify iSCSI Target Configuration

  4. Check iSCSI Initiator Settings

  5. Reboot the QNAP NAS

    Ensure no active data transfers before rebooting.

  6. Update QTS and iSCSI Drivers

    Back up your NAS configuration before updating firmware.

  7. Contact QNAP Support

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When to Call a Professional

If the error remains after all steps, the iSCSI target may be faulty or the network infrastructure may need professional assessment. Contact QNAP support or a network specialist.

Frequently Asked Questions

What does QNAP error 40 mean?
Error 40 indicates an iSCSI initiator timeout, meaning the QNAP NAS lost connection to the iSCSI target. This is usually caused by network issues or misconfiguration.
How do I fix QNAP iSCSI timeout?
Start by checking network cables and restarting the iSCSI service. Then verify target settings and reboot the NAS if needed. Updating QTS firmware can also help.
Can I recover data after error 40?
Yes, error 40 does not cause data loss. Once connectivity is restored, iSCSI sessions should resume normally. However, ensure no data is being written during the timeout.
Do I need to reconfigure iSCSI after error 40?
Usually no. Simply restarting the iSCSI service or rebooting the NAS re-establishes the connection. Only reconfigure if you changed settings or the target IP changed.
Is error 40 hardware related?
It's rarely a hardware issue. More often it's network cables, switch problems, or misconfigured settings. Check cables first before suspecting hardware failure.

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