This seems to be a software issue, not an IRS/SSA e-file issue. Simply editing the return to unmark the spouse as deceased and re-filing will result in the return being accepted. This was not an issue when using the 2018 version of TurboTax. I filed the same sort of return for my in-laws last year for a husband who had passed in 2017, and it worked fine with one spouse marked as deceased.
My guess is that TT is simply not sending the AGI and/or PIN for a deceased spouse on a joint return in the 2019 version of the software.
Also, as others have pointed out, printing and mailing is not a great solution *after* you have already paid the $25 e-file fee.
