FYI, I did not the following in order to get it to work:
1. In the Schwab Security Center I toggled the 3rd party app support off/on a couple of times
2. Since I am MacOS based in Safari Preferences I enabled popups for all apps
3. Restarted TurboTax and tried again. This was critical.
It worked!
* Don't forget to change your popup settings back to Block or whatever your old setting was after you finish the download of your 1099 data.
