I called TurboTax support yesterday and we fooled around with it a bit, deleted browsing history and cookies, all to no avail. The 1st level guy on the phone hadn't heard of the problem, and his 2nd level contact had no ideas (other than the clear history stuff).
So I looked around a bit harder and found a reddit post that said installing all the latest MS updates (to Windows 11) fixed the problem. I hadn't done an update in a couple weeks, so needed to anyway. So I installed KB5051987 Cumulative Update for W11 V 24H2 and KB5049622 Cumulative Update for .NET Framework 3.5 and 4.8.1 for W11 V 24H2.
Tried the 1099 download again, and it worked. So that's 2 success cases; maybe it'll work for you!
