Hello

This error could be caused if all the required JLive! Chat javascript files aren't loaded into your website by the JLive! Chat plugin.
Please ensure you have the latest version 4.0.5 JLive! Chat component, plugin, module and desktop application installed. You can check the version you have installed by going to Extensions -> Install/Uninstall -> Components from within your Joomla administrator.
I checked out your website, but the issue didn't error didn't occur for me, probably because you disabled proactive chat. Please confirm you have the latest version component, plugin, and module installed and then enable the proactive chat feature, and if you still get the error, let me know and I will check it out ASAP.
Thanks!
John