The only way you can get your third stimulus check is through your 2021 tax return. The stimulus money is added as a refundable credit. However, if you owe taxes, the stimulus money would be used to pay any taxes owed on your return. You will not receive a check for the full amount of the stimulus funds, only whatever your refund is if you have a refund.
Since I do not know what the IRS indicated was wrong with your return, it sounds like you need to amend your return according to what the IRS said was wrong.
