# 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.
**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)*.* |
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