# Troubleshooting spent reagent cartridge not detected on NextSeq 500/550

**Background** The NextSeq 500/550 instruments divert used reagents to the spent reagents cartridge for storage until the user empties it after sequencing runs complete. If the spent reagents cartridge is not detected, the Control Software will alert the user. The *Unable to detect spent reagent cartridge* error on the NextSeq 500/550 indicates the instrument cannot detect the spent reagent cartridge is present. This error appears when: \* The instrument does not register the spent reagent cartridge during pre-run checks

* The instrument fails to detect the spent reagent cartridge is present while setting up a wash or a sequencing run
* The instrument registers there is a spent reagent cartridge inserted even when it is taken out

If receiving a “spent reagents cartridge is full” related error, please see article: [Troubleshooting spent reagent cartridge is full on the NextSeq 500/550](https://knowledge.illumina.com/instrumentation/nextseq-500-550/instrumentation-nextseq-500-550-troubleshooting-list/000001392/?utm_source=agent\&utm_medium=email\&utm_campaign=kb).

**Troubleshooting Actions**

1. Power cycle the instrument to reset the sensor communications.
   1. From the instrument home screen, select **Manage Instrument**.
   2. Select **System Shut down Options**.
   3. Select **Shut Down** (this will shut down software and turn off instrument power).
   4. Wait two minutes before turning on the instrument from the button in front.
2. If the error message continues to appear, contact [Illumina Technical Support](mailto:techsupport@illumina.com) to determine the next steps.

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| *For any feedback or questions regarding this article (Illumina Knowledge Article #1689), contact Illumina Technical Support* [*techsupport@illumina.com*](mailto:techsupport@illumina.com?subject=Question%2FFeedback%20Regarding%20Illumina%20Knowledge%20Article%20#000001689%20-%20Instrumentation%20\&body=Dear%20Illumina%20Technical%20Support,%0D%0A%0D%0A)*.* |


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