open support ticket it can be many reasons:
What is your request volume for the service? Sometimes it can be just the throttling Dynatrace has (won't capture PurePaths above 1000 reqs/min) - this limit can be tuned in CMC for Dynatrace Managed.
Other reasons typically include some sort of cookie or header filtering. Dynatrace correlates web requests from browsers by cookie values.
Actually, it's per process not per service. But I'm not sure whether this is your case. If possible I'd recommend to try to find a purepath from the user action by other means (such as URL parameters). If you can find it, then it's not the case of adaptive capture control.