Paprika now uses system notifications to play timer alarms. You will need to make sure notifications and sounds are both enabled for Paprika 3 under iOS Settings -> Paprika 3 -> Notifications.
Also, make sure your ringer volume is turned up under Settings -> Sounds -> Ringers and Alerts. iOS has two separate volume controls: system volume and ringer volume. Typically, system volume is controlled by the physical buttons on your device, whereas the ringer volume is controlled either in Notification Center, or under Settings -> Sounds -> Ringers and Alerts.
Finally, make sure that the physical mute switch on your device is not set to mute, and that Do Not Disturb is not enabled under iOS Settings -> Do Not Disturb.