Notifications can play a key role in Star Trek so we recommend you to have them turned on in the game. In order to do that, you need to access your in-game profile avatar:

Go to Settings:

and click on Notifications.

You have done it!

(Android users only) If this is not working, you must turn on the  Notifications of your Star Trek App settings on your Android. These settings may change after a game update, so check on that even if you have done it before.