I'm having same problem. I need to use the turbotax app because the online turbotax doesn't know how to handle backdoor Roth IRA contributions. Online version reads in Merrill Lynch statements fine. The Mac app can't open the Merrill Lynch account. Note, it only has Merrill Edge option which is NOT Merrill Lynch account. I bought the App because the online version can't handle backdoor Roth conversions, but the app can't read in my brokerage accounts.
