Thanks for the advice, but in my case it doesn’t help. I changed the paths, but it did not change anything. I still get error.
I tried to use the demo plugin (https://github.com/mattermost/mattermost-plugin-demo) and it works well.
I get an response Hello World! to the request /plugins/com.mattermost.demo-plugin/hello
I can’t understand the reason for this behavior. Now I decided to use the demo plugin as the basis.