Command returns usage /<command>

Hello. Faced a problem: when entering a command, it returns usage. If you remove usage, then nothing is returned. Tried a lot, nothing helped. Help me please. There are NO any errors in the console.

Main.java

Code:

package ru.belevich.parkour;

import org.bukkit.Bukkit;
import org.bukkit.plugin.java.JavaPlugin;

public class Main extends JavaPlugin {
  
    public void OnEnable () {
        Bukkit.getLogger().info("PARKOUR V 1.0 ENABLED!");
        Bukkit.getPluginManager().registerEvents(new Events(), this);
        getCommand("maxparkour").setExecutor(new CommandManager());
    }
  
    public void OnDisable () {
      
    }
}

CommandManager.java

Code:

package ru.belevich.parkour;

import org.bukkit.ChatColor;
import org.bukkit.command.Command;
import org.bukkit.command.CommandExecutor;
import org.bukkit.command.CommandSender;
import org.bukkit.entity.Player;

public class CommandManager implements CommandExecutor {

    @Override
    public boolean onCommand(CommandSender sender, Command cmd, String label, String[] args) {
        if (!(sender instanceof Player)) {
            sender.sendMessage(ChatColor.RED + "Only players can use this command!");
            return true;
        }
      
        if (cmd.getName().equalsIgnoreCase("maxparkour")) {
            sender.sendMessage(ChatColor.GREEN + "<----- Max Parkour v1.0 ----->");
        }
      
        return false;
    }

}

plugin.yml

Code:

name: MaxParkour
version: 1.0
main: ru.belevich.parkour.Main

commands:
  maxparkour:
    description: Max Parkour main command
    aliases: [mp]
    usage: /<command>

 

inside of the if statement type in "return true;"