AJAX call inside plugin class is not getting to it’s response function

Problem seems with build_a_boat() function. You called that function from inside a template file. Does that gets called on the desired page load?

Solution: Try to call that function from plugin root file. Also add that function in root file to ensure the call is working.

Try by adding this in plugin root file.

function build_a_boat(){
    // blah blah blah
    require_once BUILDNEWBOAT_PATH . 'includes/BuildNewBoatPlugin.php';

    $build_boat_plugin = new BuildNewBoatPlugin();
    $build_boat_plugin->run();
}

build_a_boat() // call to the function