@anthony340 - What begs your question?
The deadline to submit a tax return (or an amendment) for the purpose of obtaining a credit is three years after the due date of the original return. So unless you originally filed for an extension of the 2019 tax return, the due date that year was July 15, 2023 (it was delayed due to the pandemic from April 15).
if you owe taxes, there is no deadline, you always owe until the liability is satisified.
if you fail to claim the carry loss forward via an amendment of you 2019 tax return prior to July 15, 2023, I can't imagine you are able to take the adjustment in a future year. The IRS would have no record of it on your 2019 tax return, so why would they accept it in 2020 (or any future year).
