# How to resolve 'An unknown error has occurred' critical system errors on the NovaSeq X Series Instruments NovaSeq X Series Control Software initialization issues that do not fit within the Control Software error reporting structure will present with the following error message: ![](https://761066130-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FGM9W2DuBTgEXv1ClCm8H%2Fuploads%2Fgit-blob-ad1343657f75f19073619bf168680b05a02327e8%2Fimage1.png?alt=media\&token=96953e5e-0b3e-4645-bda5-83953ea74a0c) "Critical system error - An unknown error has occurred. The system may require a restart." If this error presents during instrument or Control Software initialization, see the following recommendations: **Troubleshooting Actions** 1. Do not select Shutdown or power cycle the instrument. Instead, select **Exit Application** to close the NovaSeq X Series Control Software. 2. Collect the Control Software Logs from the /usr/local/illumina/logs/novaseq-x-series-control-software directory on the instrument. 3. Contact [Illumina Tech Support](https://www.illumina.com/company/contact-us.html) for next steps. \ \ \
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