I had this problem back in March 2018 when I did my 2017 taxes.I advised Turbo Tax of the problem and they told me to talk to TD Ameritrade Institutional....who...

I tried using my account number and doc ID - it didn't recognize me as a client

I couldn't download my info from TD Ameritrade Institutional and had to do it all manually.I hope this is fixed for 2018 returns.