1. Turn on the phone. When we install some software, we will encounter the problems shown in the figure.
2. Next, find the setting tool, as shown in the figure below.
3. Next, you need to click Security and Privacy, as shown in the figure below.
4. Next, you need to choose more security settings, as shown in the figure below.
5. Here, click the button behind the external source application to open it.
6. At the same time, turn off the external source application check.
7. Finally, try to install a certificateless tool, and you can solve it. An example is shown in the figure.