I had the issue where I would click the 'Get Form' button to connect specifically to Charles Schwab and the pop up was a square screen that was completely blank. I have the desktop version of TT. I had seen that others has mentioned changing your screen resolution, so I changed my resolution to anything other than what it was, then my PC said 'do you want to keep this resolution or revert?' I clicked 'Revert'.
Magically, now the blank TT screen was showing the login screen for Charles Schwab. I had also seen someone say that if this happens you still cannot interact with this pop-up window, which was also true for me. However, I blindly clicked into the Login ID box and typed my ID in. The screen showed nothing, but if I did the 'change screen resolution, do you like it, Revert' "cycle" again, then the TT screen refreshed and I could see what I typed.
I was able to log into Charles Schwab, accept their Terms and Agreement, select which forms I want, and agree to connect these accounts to TT, and at _every_ step in the process I had to do the "cycle". It did work for me and I was able to import information into my TT.
I hope this solution works for others, this was very frustrating.
