You cannot start a new 2019 tax return in TurboTax Online after October 15. You could use the CD/Download TurboTax software, but you have to pay for it. You can purchase a download at the following link.
Past Years' Products
You might get a better price from a reputable online seller that still has TurboTax for 2019 in stock.
It's also too late to e-file a 2019 tax return. Your nephew will have to print his 2019 tax return, sign it, and file it by mail. The IRS stopped processing mailed tax returns for several months because of the Covid-19 pandemic. They recently started to process them again, but they have limited staff and a huge backlog, so it will be quite a while before your nephew's tax return is processed.
