Plugin is good but License not working

We like this plugin, it is working as desired but even though we bought the premium version the support is limited and they haven’t answer my email. I have the same problem as Bobbi, can’t make my license code work and there is a notice in WP saying:

“The SIP Advanced Email Notifications for WooCommerce API License Key has not been activated, so the plugin is inactive! Click here to activate the license key and the plugin.”