> 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/000001684.md).
# Troubleshooting an initialization failure due to Proxy warning on the NextSeq 500/550
The NextSeq Control Software (any version) may fail to initialize due to a Proxy System blocking access to IP addresses required for hardware communications. Internal Network Interface Card (NIC) and the system's Main Printed Circuit Assembly board must be given proxy "exceptions" to operate normally.
The error messages may appear as follows:
* "*Failed to communicate with firmware via FTP at 'XXX.XX.XXX.X'. This may be caused by incorrect Proxy Settings. If the instrument is using Proxy Servers for LAN, ensure the IP Address...*"
* "*The remote server returned an error: (500) Internal Server Error.*"
**Troubleshooting steps:**
1. Exit the NextSeq Control Software.
2. Navigate to the **Control Panel** > **Internet Options** > **Connections Tab** > **LAN settings**.
3. If "Use a proxy server..." is checked, select **Advanced**.\
4. Enter the appropriate IP address in the **Exceptions** field. Separate each IP with semicolons.
* 192.168.113.2
* Depending on which instrument/control software, add the following IP address as well:
* | Instrument | IP Address |
| --------------------------------------------- | ------------- |
| Windows 7 (NCS v2.2 or below) | 192.168.113.5 |
| Windows 10 (NCS 4.0+ without Airflow upgrade) | 192.168.113.5 |
| Windows 10 (NCS 4.0+ with Airflow upgrade) | 192.168.113.3 |
* If in doubt, contact [Illumina Technical Support](https://www.illumina.com/company/contact-us.html#/) for additional assistance.
5. Select **OK** and close all control panel boxes.
6. Restart the NextSeq Control Software.
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| *For any feedback or questions regarding this article (Illumina Knowledge Article #1684), contact Illumina Technical Support* [*techsupport@illumina.com*](mailto:techsupport@illumina.com?subject=Question%2FFeedback%20Regarding%20Illumina%20Knowledge%20Article%20#000001684%20-%20Instrumentation%20\&body=Dear%20Illumina%20Technical%20Support,%0D%0A%0D%0A)*.* |
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