This is on my signature page. Not amended return. Under penalties of perjury, I declare that I have filed an original return and that I have examined this amended return

You have to be looking at the Form 1040-X and not the Form 1040

If you are e-filing your 2024 tax return there is no physical signature to be entered on the federal tax return, Form 1040.  You have to enter the 2023 AGI and a 5 digit self-selected PIN to e-file the 2024 return.

Why does the 2024 TT program not accept the 5 digit PIN for the e-file signature?

NO, its a 1040Sr...one spouse is now deceased. Does that complicate things?

Turbotax wants a PIN to SUBMIT your return. Choose a new PIN .enter AGI.

TurboTax doesn't support prior year PIN.