Fatal Error in Wordpress Plugin

Hi all,

I am building my website using WordPress and I have installed a plugin called "MQTT-Cogs", when I try to active it, I get this fatal error:

Fatal error: Uncaught Error: Class "sskaje\mqtt\MessageHandler" not found in C:\xampp\htdocs\smart_home\wp-content\plugins\mqtt-cogs-3.0-alpha\MqttCogs_Plugin.php:1969 Stack trace: #0 C:\xampp\htdocs\smart_home\wp-content\plugins\mqtt-cogs-3.0-alpha\mqtt-cogs_init.php(24): require_once() #1 C:\xampp\htdocs\smart_home\wp-content\plugins\mqtt-cogs-3.0-alpha\mqtt-cogs.php(100): MqttCogs_init('C:\\xampp\\htdocs...') #2 C:\xampp\htdocs\smart_home\wp-admin\includes\plugin.php(2288): include_once('C:\\xampp\\htdocs...') #3 C:\xampp\htdocs\smart_home\wp-admin\plugins.php(192): plugin_sandbox_scrape('mqtt-cogs-3.0-a...') #4 {main} thrown in C:\xampp\htdocs\smart_home\wp-content\plugins\mqtt-cogs-3.0-alpha\MqttCogs_Plugin.php on line 1969

Can you please help me to fix this error?

Here you can see the plugin file: https://github.com/ciknowles/mqtt-cogs

Thanks.