You need to specify the events which you want your bot to receive using gateway intents.
Instead of
const client = new Discord.Client();
Use
const client = new Discord.Client({ intents: [Enter intents here] })
For example
const client = new Discord.Client({ intents: ["GUILDS", "GUILD_MESSAGES"] })
Here’s another useful link: https://discord.com/developers/docs/topics/gateway