For Merrill, I saw another user changed their password for Merrill and then was able to import. Let me know if this works for you.
User solution:
The ultimate solution, although I do not understand why, was to change my Merrill password. Once I did this, the import worked fine. My previous password worked in Merrill, but for some unknown reason when I used the same ID/Password in TurboTax, I could not log in.. Simply changing my password in my Merrill account and then attempting the import with the new password worked.
I tried changing my MyMerrill password on the MyMerrill website today, however, after doing that, I am still unable to login to Merrill - Merrill Edge in TurboTax Home and Business. The popup message I keep getting in TT when attempting to login to Merrill is: "Please attempt your login again. If you continue to have difficulty, please call 1.800.MERRILL (637.7455)." I'm wondering if there is a difference between MyMerrill and Merrill Edge that TurboTax does not seem to know about.