Debug Logging not working
The plugin seems to have custom debug logging in the plugin. This can be enabled in Follow-Up Emails > Settings > Tools.
I set this to Log to File = All
I then tried scheduling emails, sending scheduled emails. Sending manual emails, and several other actions. But the log file always seemed to remain empty. I can see the file `wp-content/uploads/fue.log` but it remains empty.
I'm not sure what should be logged in the debug logging, but it would be helpful if it would at least log something.
Might also be worthwhile to switch to the WooCommerce logger: https://docs.woocommerce.com/wc-apidocs/class-WC_Logger.html