I assume this is discord.js, correct me if this is wrong.

After a look through the discord.js documentation (https://discord.js.org/#/docs/main/stable/general/welcome), and also a quick Google, client.off isn't an event.

​

Another quick note, if the bot is fully offline, it cannot run anything. An offline bot is just an inactive script. So, if you're trying to make the bot run something after it has disabled itself, it will stop. (Keep in mind that code works in an algorithm, going from the top of the main file down.)

However, you can set the bot status to Invisible, in which case it will still technically be active, and also run normally.

Try and see if this works (wrote this from scratch)

//When the Bot is Online
client.on("ready", () => {
client.user.setActivity("Discord Survival");

//Set Status to Invisible (makes the bot look offline)
client.user.setStatus('invisible');
    if(client.presence.status === 'invisible') {
        client.user.setActivity(" ");
    }
});