I'm sorry I'm not fully following what you are saying...
You say, you don't know what happened, then go on to say, I tried to remove the option....
So did you try to turn off the alert and this was the result or was turning off the alert your attempt at getting it back?
If you made a change and it stopped try reversing the change. If you don't want audible alerts from the app set the sound for the app to silent.
Have you checked the notification settings for the app? If you go into the device Settings>Applications and notifications, scroll to the app page, open notifications and be sure that app badges are turned on.
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