You must enable the auto start to the apps that you want to show notification while the phone is locked,
For example, if you have problems with whatsapp notifications, you must enable the auto-start of this app. so it was solved
apparently that is the problem, the auto-start of whatsapp and other apps were disabled, thank you very much !!!
I only have the doubt of the cause of this, everything worked normal until version 20.8.13
Thanks again
Notifications do not work, only when I unlock the phone the notifications arrive all at the same time, this problem is from the previous update 20.8.13
i have a mi 9t pro