To stop churn, you need to attract customers who won't leave. That sounds counterintuitive, but that's the best way to actually stop churn.
Fix retention by fixing acquisition
Growth → Retention & Engagement
It's usually the step right before conversion. So if they aren't sure why the user opens the app or they aren't sure why the user got to this checkout page, it's often some copy or the path has been ineffective in some way.
Working on early user experience is highly impactful. You often see product teams say we should work on resurrection because we have this huge pool of users that is churned out. If we get just 1% of those people back, it's going to be such a big lift. The problem is that pool of users is the group of people who has tried the product and decided they don't want to use it.
Rarely should you go right to the source and send them more email or push notification or something like that. It's really actually about understanding what is the customer experience and what matters to them.