Nosto triggered email feature requires customers to activate a certain trigger before emails are been sent while obviously you need to enable the feature first.
Further, customers also need to be identified by Nosto. Immediately after Nosto has been implemented, only a small number of email addresses have been collected, consequently only a small share of visitors can be identified. This basically means that not all customers or cart abandoners are identified by an email address, which explains often a notable difference between abandoned carts and sent abandoned cart emails. As an easy trick to enhance number of emails sent, you should encourage and entice customers to register and log-in which increases the amount of identified customers.
As a suggestion few tips & tricks below to increase the number of registered customers.
Enable Pop-up features, especially follow-up abandoned carts
Place the login on top right and highlight visually
For new visitors offer a one time discount with a promo code
For old customers offer a free shipping or small discount if they login
Run a raffle for registered users
Start content marketing and require an email to receive material
Send newsletters that are valuable for customers e.g. promo codes, exclusive deals
If no emails are sent at all and you have a notable amount of traffic, it’s advisable to review that the implementation is done correctly. Review the login-area tagging and order confirmation page tagging by using the debug-tool and track that the customer email address is mapped accordingly. Also, you should review if the marketing permission tagging is in place correctly.