When people sign up and disappear, it is tempting to add reminders, improve onboarding or build a new feature. Start by locating the exact moment when the product stops being useful.
Look at the whole first journey.
Trace what a new user expected before they arrived, what they tried to do, whether they reached a useful outcome and what reason they had to come back. One funnel number rarely tells the whole story. Pair the numbers with conversations or observations from people who left.
Ask what changed for the user.
What problem brought them in? Did your product solve it well enough to matter? If it did, is that a problem they have again? If it did not, what got in the way? These questions point to different actions. A confusing first step is different from a product that solves a one-time problem.
Run one focused test.
Pick the most plausible explanation and write down what you would expect to see if it were true. Then test it with a small group of users before redesigning the whole experience.