The error indicates the shortage of funds in the user’s Metamask account:
a) for a gas fee to complete a transaction;
b) for the agreed amount to transfer into the contract (after deployment).
c) because the token indicated in the contract does not match the token in your Metamask account.
What you can do to fix it:
Step 1. Make sure you have in your Metamask account the token selected for the contract (a stablecoin).
Step 2. Check if you have enough native tokens of the selected network (ETH for Ethereum, or MATIC for Polygon, for example) to pay the transaction gas fee.
Step 3. Add funds to your Metamask account to cover the gas and transferrable amount of stablecoins (only the buyer transfers the agreed amount).
Step 4. Re-login or refresh the page and try to perform the transaction again.