# Troubleshooting ### Unable to Achieve Contact Quality on Any Channel There could be two reasons for this happening: 1. The sensor trees are not plugged into the FLEX controller; or 2. The reference sensors are not connected to your participant. Please make sure there is contact with both DRL and CMS. ### The Input Channel is Always Black There could be two reasons for this happening: 1. There is no contact quality (see above); or 2. There could be an error with your FLEX Controller. If this is the case, please contact [EMOTIV Support](https://www.emotiv.com/contact-support/). --- # Agent Instructions: 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: ``` GET https://emotiv.gitbook.io/flex-2.0-user-manual/support/troubleshooting.md?ask= ``` The question should be specific, self-contained, and written in natural language. 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.