This error could have occured if the configuration of the data source is incorrect. I would perform the following checks to establish a successful connection.
* Check the host name or ip address provided in the connection URI
* Ensure that the MYSQL server is started and running
For more information, refer to the similar community [here](https://community.denodo.com/answers/question/details?questionId=9060g000000XexiAAC&title=Failure+to+continue+the+community+tutorials).
Starting from Denodo 7.0, our recommendation for doing the labs is to use the Denodo Quickstart Virtual Machine. All the data sources needed for doing the labs are already available in the Virtual Machine, you just need to download and configure the VM and when it is running you will be able to do all the labs. Refer to the **Configuration** module of the on-demand course for information related to Virtual Machine.
Hope this helps!