Read the rejection message. It tells you why it was rejected. Sometimes not with much clarity though. So if you need help understanding the reason it was rejected, then tell us the rejection message or code you got.
Bottom line is, you had to pay your TTX fees in order to transmit the return to the IRS. Therefore, the option to clear and start over is not available, and never will be. You just need to fix the reason for rejection, and then click that big orange TRANSMIT RETURNS NOW button again.