Now this issue could be caused by several reasons. Here are some suggestions to make sure this feature works without any troubles:

1.  SMTP configuration: This is the most important part. You should make sure that the SMTP configuration in your site is working. You can use this plugin ( https://wordpress.org/plugins/wp-mail-smtp/ ) to test the configuration. This will help to solve your problem. You can test your SMTP configuration by sending a test email with the plugin. If the mail is sent then the SMTP is configured properly, if not then you need to set up the SMTP.
   
2. Invalid Email: This could also be caused by adding an invalid email account in the Notification settings. Please make sure the email address/es you have added is/are valid.
   
3. Store Entries Option: Please keep the Store Entries option enabled. We recommend keeping that option always enabled because this function is required for “Confirmation”, “Notification” and other functionalities to work. Please see the screenshot ( https://d.pr/i/ELI9s6 ) to be clear about where to find it.
   
4. Cache: Please make sure to clear all the cache from your website including any plugin, browser, server, or CDN (e.g. Cloudflare) also try disabling the Cache/Optimization plugin for some time if you are using one.
   
5. Recaptcha: This issue could also be caused because of an invalid recaptcha configuration. You can find the proper instructions in this doc – ( https://wpmet.com/doc/recaptcha-integration/ ). Make sure to configure it properly.

If you still need any assistance regarding this matter please create a support ticket from this link – https://wpmet.com/support-ticket-form/. We will help you solve any problems.