I had my first customer upgraded to the latest version of Business Central the other day. But after the upgrade was complete i was unable to log onto Business Central. The Dynamics logo was just flashing on my screen. So again i went to Twitter for help.
What i had to do to solve the problem was to clear the cookies in my web browser. For those of you who do not know how to do that you open your web browser and click CTRL+SHIFT+DEL
That shows you this dialog box. Where i checked only cookies and other site data. That helped solve the problem for me. But i kept getting support calls from other users that was not able to log on to Business Central even after clearing cookies. So for those users we had to clear all the browser data before they could log on.
I hope your upgrade to the latest and greatest version of Microsoft Dynamics 365 Business Central runs smooth with out any issues. But in case you run into something it can be a good idea to clear your browser data.