Good evening and welcome back!
Thank you for reaching out to us.
We are sorry to hear about the email not being sent out to the participant. Yikes!
I would love to help you with this topic.
As a first troubleshooting step, could you please provide us with your complete system information in a private reply using the instructions found in the following link?
https://theeventscalendar.com/knowledgebase/sharing-sys-info/
One sure way to solve that type of issue is to have the system send tickets from any chosen email address by simply installing, configuring and testing the following plugin: https://wordpress.org/plugins/easy-wp-smtp/
Using a real SMTP server with authentication will bypass the built-in WP mail functionality altogether.
Please make sure you configure and test the settings using the plugin’s built-in tool.
Hang in there!
Geoff B.