Program not working as expected on DigitalOcean Ubuntu

Question

Currently, I am writing a discord bot on python and tried to put it on my droplet of Digital Ocean to make it run 24/7; however, my play method and radio method will not produce sound in the environment. When I tested on my local python interpreter everything works fine but the statement seems to have no effect when it was run on the server.

    @commands.command(name="radio")
    async def radio(self, ctx, url: str = 'https://listen.moe/fallback'):
    print("radio received!")
    channel = ctx.message.author.voice.channel
    self.is_radio = True
    try:
        self.vc = await channel.connect()

    except Exception:
        pass
    if self.vc is None:
        await ctx.send("Sorry but I cannot find where are you...")
    else:
        await ctx.send("Take a look at this! Hope you will like it~")
        self.vc.play(FFmpegPCMAudio('https://listen.moe/fallback'))

I uses the ubuntu provided by the Digital Ocean droplet, and uses git clone to copy the file into the server, then uses python3 main.py to run the code.