Thanks, TomK. Nowhere did I find anything in online TurboTax to indicate which form was the problem, reviewing the entire return turned up nothing. Resolved problem by using H&R Block desktop software, which (1) still works on Windows 10, (2) had NO problem transmitting any of my data, and most fun of all, (3) confirmed to me on Jan 22 that the IRS had indeed accepted my submitted return. After using TurboTax for more than 15 years, I’m changing platforms to one which better serves my needs, not the other way around.
