Is the IRS saying you didn't pay or you owe more? How did you pay? Did you mail a check with a 1040-V voucher or use a 1040ES slip? Your only proof is your bank statement or credit card showing the payment. If the IRS changed your return how much more do you owe? A common adjustment is if you claimed the Recovery rebate credit on 1040 line 30 when you already got the first 2 Stimulus payments or got the second one after you filed or reported the wrong amounts or entered them in the wrong box. Do you have an amount on line 30?
