You need to inspect the system status page in WooCommerce to check if there's anything not functioning properly?
Then ensure Is it actually a WooCommerce problem, or if for example sendmail() is not working. To check this you can see your PHP settings or request a password change for your account and see if that email does arrive.
In WooCommerce this issue arises, when the woocommerce_defer_transactional_emailsfilter has been introduced. Try and see if that's the issue by disabling it using this code:
add_filter( 'woocommerce_defer_transactional_emails', '__return_false' );
Still facing the issue you need your email back up and running asap I would suggest setting up a transactional email service such as Postmark. Such services have always been the most trustable.
