> 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/000007435.md).
# 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.**
\
\
\
| |
| :--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------: |
| *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)*.* |
---
# Agent Instructions
This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com.
## Querying This Documentation
If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.
Perform an HTTP GET request on the current page URL with the `ask` query parameter, and the optional `goal` query parameter:
```
GET https://knowledge.illumina.com/instrumentation/nextseq-500-550/instrumentation-nextseq-500-550-troubleshooting-list/000007435.md?ask=&goal=
```
`ask` is the immediate question: it should be specific, self-contained, and written in natural language.
`goal` is optional and describes the broader end goal you are ultimately trying to accomplish on behalf of the user. GitBook uses it to tailor the answer towards what is most useful for that goal.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.
Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.