If your child didn't stir, that is ok. This can occasionally happen! Just tell the app and you are done for the night.
However, if you haven't seen your child stir in bed or show any movement for a few nights, then it may be time to increase the vibration strength. Access the vibration settings in the app. Select the menu icon on the top left, select User Settings, and then select Adjust Vibration Level.
If the level is already set to the maximum, we recommend moving the Sleep Guardian closer to either your child's torso or head.