Notifications may not be working because the email authentication setting is turned on. Please make sure this setting is turned off for your site by doing the following:

1. Go to your website's Dashboard
2. WP Mail SMTP
3. Settings
4. Got to the Other SMTP section
5. Make sure Authentication is turned OFF.
6. Click on "Save Settings" to save your changes.

Once this is turned off, you will be able to receive notifications from form submissions again.