Called TT support and reported, was eventually told it was due to not having the updates from the IRS, which the expect today Jan 26 2026. Checked software version, no updates available. Installed on Jan 25 2026 from download. Support said this problem and others are expected to be patched and he would send a list of areas not yet completed for the desktop version via email. (No email arrived, but I did get a survey for the call).
Anyway, the solution for me was to go to the form, social security - open it - scroll down - delete it, then go to step by step, click update on the section, and voila, I could enter the data.
fyi It appears this problem existed last year and still hasn't been fixed, so try this as a temp fix
