No that wouldn't be the reason.  Are you trying to transfer from your computer into the online version?  Are you trying to transfer the file ending in .tax2019?  Or the pdf?

pdf return

I wouldn't bother trying to transfer from a pdf.  It only transfers very basic info like your name and address and AGI.  Did you use Turbo Tax last year or is it another pdf? It has to be an electronic pdf file not one you scanned in.  If you used Turbo Tax you should have a data file ending in tax2019 on your computer or be in the same online account and it will automatically transfer.