There may be one or more reasons for this, it should be checked one by one and the steps should be applied one by one.

• Go to settings>enter app settings>find NotifySave>click on storage>delete all data.

1. Disable the Battery optimization option that appears when the app opens.
2. Then allow the app to monitor your notifications.
3. Make sure auto start is turned on.
4. If you can't do these steps, I'll leave articles on how to do it.
If you do all this and your problem is still not solved, you can leave us feedback.

Turning on auto start:

https://apptosd.com/en/article/how-to-turn-on-automatic-startup-for-xiaomi-devices

https://apptosd.com/en/article/how-to-turn-on-automatic-startup-for-huawei-devices

Turning off battery optimization:

https://apptosd.com/en/article/how-to-turn-on-automatic-startup-for-huawei-devices

https://apptosd.com/en/article/how-to-turn-off-battery-optimization-for-xiaomi-devices