Board Thread:The Quarters - Q & A/@comment-29119829-20160717222614/@comment-24672610-20160718024158

It could be a result of your android device's notification settings. Maybe you had notifications turned off at that time, or the Habitica app doesn't have permission to send notifications?

If you think this is a bug in the app and not just a settings issue, report it through the app at Menu > About > Report a Bug so the developers will see it.