Oh are your or your spouse over 65? Did you file a 1040SR return instead of the plain 1040? You can't transfer a 1040SR pdf.
How to Transfer from a pdf into the Windows Desktop program
https://ttlc.intuit.com/community/using-turbotax/help/can-i-transfer-last-year-s-pdf-into-the-turbot...
You can Transfer a PDF into Windows Desktop if your 2023 PDF is a 1040 return generated through TurboTax, H&R Block, or TaxACT software (Form 1040-SR is not supported for PDF transfer).
Be aware that in some cases TurboTax won't be able to read the PDF, for example if it's password-protected or is a scanned copy of a PDF instead of an actual PDF file.
