The previous version had a similar problem.
That problem was somehow resolved by changing the windows theme. If your windows theme is "windows basic", it doesn't load; if you change the theme to anything else, it logs in.
Try it and revert with your feedback.
There was a weird problem with ZT for me... After ZT was installed, when I created a shortcut to my desktop with the main exe being checked to run as administrator and compatibility changed to Windows 7, if I opened ZT from the desktop shortcut, the two green buttons that display the connection status would be red. But if I directly opened it from the installation folder, the connection would be green. Weird. I don't even know how this is technically possible. We could have a Ph.D in solving Nest problems and even win a Nobel Prize in debugging, first time ever...
And, surprisingly I haven't faced a login issue at all with Pi...
Probably this would help... Once Pi is installed, go to the installation directory, change the compatibility of Pi executable to Windows 7 or your current windows version. In addition, check the run as administrator box...
If the shortcut still has a problem, run it from the installation directory...
Please post how this works out...