I am using TT Premier on a Windows PC. When I try to import my Charles Schwab 1099 (INT or B) info I end up with a blank popup window with the title "Bank Login". It is pretty hard to login with a blank page (I actually did but that is another story).
I found a hacky way to get the page to draw the UI (definitely not pretty but functional): pick a new display resolution and then revert back (changing the scaling also works but requires more steps).
The login page will draw the UI exactly once per display resolution set/revert. The page will appear non-functional but it is working just not updating the UI.
I clicked in the login field and typed in my id. The UI appears frozen but another display resolution set/revert shows my id is there.
Repeat for the password field: click and type your password in. Click on the show password "eye" if you want to see your un-obfuscated password. Again the UI appears frozen but a display resolution set/revert shows the password is there.
Click on the login button and set/revert the display resolution to see the next page.
On the next page there is a check box down near the bottom so need to scroll the page. Click and drag the scrollbar to the bottom. It will not appear to work but do a display resolution set/revert to set the page scrolled.
Continue to use the display resolution set/revert to get the page to update. Fill in the forms as necessary. Remember the window will appear not to work because it is not updating. But it was working for me.
Hacky but it worked for me.
I hope this helps
