So here's a follow-up:
TT Tech support tried to help but could not. It appears that once you change delivery method to snail-mail and fill out amended forms, the software will not permit (does not provide any way to) change back to e-file. What is maddening about this is that it was simply a typo on one SSN -- one would think this a simple thing to correct and then resubmit... but no.
