I, too, have been having this issue for last week. Using TT Premier Desktop for Mac. Specifically my issue is encountering unsuccessful outcome after entering ML login credentials to TT import screen when attempting to "establish(ing) secure connection". Activity meter goes back and forth for several seconds then nothing - some times a beep / tone. All other institutions (e.g., Schwab, Fidelity, BoA even) connect / download fine. Problem is specific to ML, though I was able to connect and download 1099s earlier in February prior to recent release of 1099s from ML last week.
Spent hours scouring online forums including TT community and it appears many people are encountering similar issue. Also spent A LOT of time on phone with TT "technical" support to no avail. Verbal response to TT investigation yielded no success, pointing to issue residing with ML. I have tasked my ML advisor to find someone within ML technical support familiar with TT secure connection functionality to troubleshoot. So far, no progress.
I have performed many of the troubleshooting actions you and others suggest - including ML password change, clearing cache / cookies (though this functionality is from TT desktop directly to ML, so no browser involved), and updating TT SW and MacOS. No change with issue.
Manually entering 100s or more of 1099B transactions is a non-starter for me. I would rather find another SW product that works OR revert to last year's tax preparer. Very disappointing!!!
