No hydration alert notifications

I installed the hydration tracking app. It worked fine for a few days. I would get hydration alerts every so often, but one day, it stopped sending alerts.

I've tried reinstalling and reconfiguring it, but it still doesn't send alerts. If I open the app, it works fine, it records correctly, but there are no alerts.

Is there anything else I can do? Or should I just wait for it to be a bug and get fixed in an update?