We no longer handle email sending for you once you connect your own email provider. Things you can check and do:
Make sure your provider does not limit the number of emails sent
The emails may end up in spam
Set a reply-to domain
Make sure your email settings are correct and up to date (especially your password)
Here are some articles to guide you:
Emails landing in spam/junk folder
What to do when emails sent using your provider are landing in spam/junk folder.
Set up Custom Reply-to Domain
You can customize this reply-to email/domain by following these steps.
Set up Custom SMTP
Follow the steps below to setup your custom email address.
Regarding Email Notifications
Email notifications are only sent when:
Someone has not seen the notifications from your workspace
Someone has their notifications preference set to "Always, even when I am online" or "Only when I am offline"
Someone is mentioned anywhere or must be following the tasks