Why doesn't the phone display WeChat or QQ phone information after the screen is locked?

There are many possibilities. First of all, you turned off the background operation of qq or WeChat, which made qq WeChat unable to run after the screen was locked. Second, even if you don't quit qq yourself, if it is a Xiaomi or Red Rice phone, it will automatically quit if it has a hidden mode. In this case, I suggest you turn off hidden mode, or just lock it in the background and let it run all the time. Third, if you turn off the screen lock authority of qq or WeChat, you can go to the notification management office and open the corresponding notification authority.