Discord bot extension runs fine but doesn't work

Question

I was able to load the extension just fine, but whenever I try it out on Discord as Qball/.Qball/_Qball, the bot won't answer.

Quokkabot.py (main)

import discord
import random
import os
from discord.ext import commands

client = commands.Bot(command_prefix = '.')

@client.command()
async def load(ctx, extension):
    client.load_extension('.cogs.Quokkabot2')

@client.event
async def on_ready():
    print('{0.user} JOINED THE PARTY!'.format(client))


client.run('token')

Quokkabot2.py (cog)

import discord
from discord.ext import commands

class Commands(commands.Cog):
    def __init__(self, client):
        self.client = client

@commands.command(aliases=['Qball, test'])
async def _Qball(ctx):
    responses = [#answers]
    await ctx.send(f'{random.choice(responses)}')

def setup(client):
    client.add_command(Qball(client))

Answer 1

Commands on a cog should be defined as instance methods on that cog.

class Commands(commands.Cog):
    def __init__(self, client):
        self.client = client

    @commands.command(aliases=['Qball, test'])
    async def _Qball(self, ctx):
        responses = [#answers]
        await ctx.send(f'{random.choice(responses)}')

Then, in your main

client = commands.Bot(command_prefix = '.')
client.add_cog(Commands(client))