Hi there!
About your error:
This error is due to a plugin parameter that is not properly setup. So open the plugin parameters and make sure you fill them all right.
I will need to take a look at screenshots of your plugin parameter.
Also, the plugin has two modes: Auto Speaker and Auto Face. You also need to make sure you are using the one you want.
About the Sample Project:
Tested on the sample project and it is working just fine. You need to make sure to set the Smart Speaker ON on the plugin manager(because it is OFF by default).
And also put the Smart Speaker on the JS folder, since it is a paid plugin, it will not come inside the JS folder of the sample project.