> For the complete documentation index, see [llms.txt](https://knowledge.illumina.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://knowledge.illumina.com/instrumentation/nextseq-500-550/instrumentation-nextseq-500-550-troubleshooting-list/000002112.md).

# Troubleshooting a flow cell registration stall during pre check on first run on NextSeq 500/550

On the first run after upgrading the NextSeq 500/550 to NextSeq Control Software (NCS) v4.0.X, the pre-run checks can take around 30 minutes to complete the flow cell registration. This is expected as the instrument will be downloading drives to perform the check.

Allow the pre-run check to continue as long as no errors appear.

If an option comes up to retry the pre-check, this can indicate a communication issue. This can be resolved by re-seating the flow cell and power cycling the instrument.

For further information, search for Knowledge Base article **How to Perform a NextSeq 500/550 Power Cycle.**

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| *For any feedback or questions regarding this article (Illumina Knowledge Article #2112), contact Illumina Technical Support* [*techsupport@illumina.com*](mailto:techsupport@illumina.com?subject=Question%2FFeedback%20Regarding%20Illumina%20Knowledge%20Article%20#000002112%20-%20Instrumentation%20\&body=Dear%20Illumina%20Technical%20Support,%0D%0A%0D%0A)*.* |


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