Good afternoon Lisa and welcome to the Events Calendar Support forum!
Thank you for reaching out to us.
We are sorry to hear that you are experiencing issues with the notifications.
I would love to help you with this topic.
Since nobody is receiving any notification, I believe it is safe to say that something is getting blocked at the WP mail level.
The solution will probably be to have the system use a real 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.
Let me know if that helps.
Have a great day!
Geoff B.