# Diagnosing Offline Devices

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Sometimes cameras are displayed in Resource Tree, but are marked with unauthorized sign (). When opening such camera, it will display NO SIGNAL. Nx Witness will then prompt the user to perform more thorough diagnostics.

IMPORTANT: Run diagnostics prior to contacting support.

Diagnostics can be invoked by pressing on the Diagnostic button on the item:

Once complete, reasons and recommended actions will be displayed:

Follow instructions to resolve the issue. If unsuccessful, contact support (see "Troubleshooting and Contacting Support"). Click Copy to Clipboard and paste the data into the message prior to sending it to support.