The official WP Twitter app has a notification bug. Some people get multiple notifications for an activity, some get none. I used to get 3-5 notifications for 1 thing. By turning off notification in the app, I started getting only 2 notification per activity. Then I reset my phone because of the "other storage" problem and I never got notifications even when turning notifications back on. About a week ago, Twitter notification started working again on my phone on its own.