What the other reply said is true, Slack by default only sends mobile notifications when you're 'away.' In addition, by default, it waits 5 minutes before sending notifications (this can be changed).
The v2 Android app is currently in beta - I've been testing it for several weeks. It's lightyears ahead of the current release version which is admittedly pretty faulty (no caching means that resumes are very slow). I've also found notifications to be more reliable. Perhaps give it another try once they ship the v2 Android app.
The v2 Android app is currently in beta - I've been testing it for several weeks. It's lightyears ahead of the current release version which is admittedly pretty faulty (no caching means that resumes are very slow). I've also found notifications to be more reliable. Perhaps give it another try once they ship the v2 Android app.