You may be experiencing any of these issues:
Calendar events on your phone only give you a reminder one time after hitting snooze.
After receiving event reminders and hitting snooze you don't get any further reminders at the time of or after the start of the event.
Snooze will not trigger a notification on or after the scheduled event time. The snooze time is 15 minutes as designed and is currently not adjustable. However, the default reminder time is also 15 minutes, but this can be changed. Reminders for events can only occur before the start of the event. Once the event has started, the reminder will not trigger anymore.
For example, if you set a reminder for 30 minutes, for an event scheduled at 10:30, you will only get a reminder at 10:00 and 10:15, not at 10:30 or any time thereafter.