What's wrong with the message that OPPO R9s doesn't remind?

This is because the SMS reminder notification is not turned on.

OPPO R9S mobile phone open SMS reminder notification method is as follows:

First, click "Settings" on the desktop of OPPO R9S mobile phone.

Second, after entering the settings, select the "notification and status bar" option.

Third, find the item "Notification Management" and click Enter.

Fourth, select the "information" option after entering.

5. Then turn on the "Allow notification" switch and let the mobile phone remind you when you send a text message.