> For the complete documentation index, see [llms.txt](https://cookbook.denovolab.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://cookbook.denovolab.com/troubleshooting.md).

# Troubleshooting

- [Calls are failure](https://cookbook.denovolab.com/troubleshooting/calls-are-failure.md)
- [Change Q850 in 4xx/5xx](https://cookbook.denovolab.com/troubleshooting/change-q850-in-4xx-5xx.md)
- [One-way Audio with SIP Client Testing](https://cookbook.denovolab.com/troubleshooting/one-way-audio-with-sip-client-testing.md): How to Overcome NAT Issues When Connecting a SIP Client to a Class 4 Switch
- [Using Zoiper to resolve NAT issue](https://cookbook.denovolab.com/troubleshooting/one-way-audio-with-sip-client-testing/using-zoiper-to-resolve-nat-issue.md)