# Troubleshooting Object Reference error on NextSeq 500/550

An "*Object reference not set to an instance of an object"* is a Windows Framework error that can occur for a number of reasons.

It is often caused by communication issues between instrument subsystems or an issue with the network connection. These can appear at any time (during setup, pre-run checks, sequencing runs, post-run washes, etc.). If during a run, this may or may not affect the run performance.

![](https://761066130-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FGM9W2DuBTgEXv1ClCm8H%2Fuploads%2Fgit-blob-c1bf6a8e5ee8437acd1130cea8fe5dc552ae6c76%2Fimage1.png?alt=media\&token=f18f29a6-baf6-4cba-9425-e863a6386e9d)

**Troubleshooting steps:**

* **If the error occurs during run setup or post run wash (not during a run):**
  1. Power cycle the NextSeq 500/550.
  2. If system initializes without issue, proceed with run setup or wash.
* **If the error occurs during the run:**
  1. After run completion, confirm run performance was not affected by error.
  2. Power cycle the NextSeq 500/550.
  3. If system initializes without issue, proceed with normal use.
* **If run was affected/stopped:**
  1. Contact [Illumina Technical Support](https://www.illumina.com/company/contact-us.html#/).

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

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| *For any feedback or questions regarding this article (Illumina Knowledge Article #7435), contact Illumina Technical Support* [*techsupport@illumina.com*](mailto:techsupport@illumina.com?subject=Question%2FFeedback%20Regarding%20Illumina%20Knowledge%20Article%20#000007435%20-%20Instrumentation%20\&body=Dear%20Illumina%20Technical%20Support,%0D%0A%0D%0A)*.* |