First of all, check your MetaMask Ethereum receiving address at https://etherscan.io/ to see what the correct balance is in ETH and ERC20 tokens. For detailed instructions, see here.
If your MetaMask Extension is displaying the incorrect or inaccurate balance for ETH or other tokens, try the steps below one by one until you see your balance correctly.
Before proceeding, make sure that you have your 12-word Secret Recovery Phrase backed up in a safe place.
1) Close down your browser where you have the MetaMask extension installed and open it again.
2) Switch networks up top by clicking on "Main Ethereum Network", selecting the Ropsten Test Network, and then switching back to Ethereum mainnet again.
3) Execute an account reset
4) Install MetaMask using another supported browser (Firefox, Chrome, Brave) from our official website https://metamask.io , and then try restoring your wallet using the 12 words Seed Phrase / Secret Recovery Phrase in case the issue is only present in the browser you are currently using.
To better communicate the importance of never sharing your Seed Phrase / Secret Recovery Phrase, we've changed the name of the phrase to "Secret Recovery Phrase". Learn more here