What? You can't enter it in the 2023 return. If you paid an extension payment for 2021 it only goes on your 2021 return. You would have to amend your 2021 return to add it. But the IRS should have caught that and added it in for you. Better check the refund you got that year and see if it was included.
How to Amend a prior year
https://ttlc.intuit.com/community/amending/help/how-to-amend-change-or-correct-a-return-you-already-...
