It seems I will have to mail my return because my ex will not provide his SSN and he's a nonresident alien. However, I can't seem to get past my personal information because the program wants me to provide his SSN before I can move on.
Please explain what your filing status is. If your spouse is an "ex" spouse why are you putting anything about him on your return? Were you divorced by the end of 2018? Are you filing married filing separately -- or did you live apart for at least the last six months of 2018 and have custody of the children? If that is the case you could be filing as Head of Household. We need more information from you. We do not understand why you are putting anything about an "ex" spouse on your tax return.
You have now posted three separate questions about the same problem. Please choose one of the threads and continue the discussion in that one thread. Stop posting multiple questions about the same issue. It's too confusing and hard to follow, and hard to see the whole picture, if information is scattered in multiple threads. If you want to add more information, answer our questions, or post a follow-up question, add a reply to the one thread that you select.