Why is MetaMask sign in account not showing the balance?

If you are planning to buy ETH tokens that can be stored on MetaMask, then I would advise you to use the Metamask Sign in exchange for the same.

MetaMask Sign in one of the secure wallets you can trust. Yes! It is reliable to millions of its users globally. It is a cryptocurrency exchange that enables you to secure ETH and does Ethereum transactions in a decentralized way by using the MetaMask Sign In and app.