I had this issue with Windows 10 and finally was able to get it to work by:

1) Dumping my cache. All of it.

2) Using the Firefox or Chrome browser

3) Setting my browser to not remember prefills on the site 'app.qbo.intuit.com'

4) Dial your in-browser security down for 'app.qbo.intuit.com' and turn off your adblocker on the site

The site does not play well with security software and some secure network software like Forti Client.