You can go to Settings find Do Not Disturb and turn it off.
You may think this is too obvious and you have turned on the notification before.
After downgrading, you can refer to Ease US Mobi Mover Free, the free i Phone manager in the market to sync data to your i Phone, like add ringtones to i Phone 7 without any previous data erasing.
Notifications are not working on your i Phone and you don’t know what to do.
In this article, I’ll show you what to do when i Phone notifications are not working.If you have tried all the tips above and the notification not working in i OS 11 still exists, you may consider downgrading i OS 11 to i OS 10, as the firmware on your i Phone, like i Phone 5S may be out of date.Please note that the i OS 11 back-ups can't be restored to your i Phone with i OS 10, therefore, please ensure you have an i OS 10 backup before you decide to downgrade to i OS 10.Go to Settings turn on Show on Lock Screen and Show as Banners.Besides, tap Sounds, if the ALTER TONES is set to None, reset it to any other way, like Note, Aurora, Bamboo or Chord.