I have a problem to install ros2 on Ubuntu20.04

[Wwj180]

Certificate verification failed: The certificate is NOT trusted. The name in the certificate does not match the expected. Could not handshake: Error in the certificate verification. [IP: 64.50.233.100 443]
正在读取软件包列表... 完成
E: 仓库 “https://packages.ros.org/ros2/ubuntu focal Release” 没有 Release 文件。
N: 无法安全地用该源进行更新，所以默认禁用该源。
N: 参见 apt-secure(8) 手册以了解仓库创建和用户配置方面的细节。

please help me

[fujitatomoya]

There is no tier 1 distribution supported on ubuntu focal anymore (i am assuming that you are trying to install Foxy that is already E.O.L), see more details for https://docs.ros.org/en/rolling/Releases.html.

The error message is CA verification failed, make sure that you have trusted CA certificates. (e.g sudo apt install --reinstall ca-certificates)