> For the complete documentation index, see [llms.txt](https://docs.exoclick.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.exoclick.com/tutorials/tutorials/publishers-tutorials/how-implement-in-stream-part3.md). # In-Stream: How to implement In-Stream. Part 3: Testing the ad zone Once your website is live with your In-stream ad zone, you will start monetizing your traffic with video ads. However, it might happen that you do not see ads in the video after implementing the VAST tag. The most common reason why this happens is because the In-Stream ad zone is receiving an **empty VAST response**. When there is no video ad to show, our ad-server replies with an empty VAST XML. However, this does not necessarily mean that your in-stream ad zone is not working. In order to troubleshoot your player for VAST compatibility issues, you need to use one of the following test codes. * **For Main category**: * **For Mainstream**: * **For third party Vast tag tools**: If your player displays ads with any of the codes above, then your integration has been made correctly. You can switch to your own ad zone and start monetizing your traffic. Remember that, even if you don't see ads in your current environment, users from other countries and devices will be monetized correctly. {% hint style="info" %} **Note**: These ad zones are for testing purposes only. Once you confirm that the pre-roll video is running correctly, you will have to replace the test zone id for your real zone id. {% endhint %} If you need additional help with this step, please contact our Customer Success team selecting **Technical Assistance** from the contact form [**here**](https://www.exoclick.com/contact/) --- # 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://docs.exoclick.com/tutorials/tutorials/publishers-tutorials/how-implement-in-stream-part3.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.