Receiving this upon start?
Firstly, be sure you are not on Windows 7 or on Windows Server 2012. Run Windows Server 2016 from now on instead.
Please also make sure your computer date time is calibrated correctly. http://time.is/ should show if your computer date time is any different to their servers.
Lastly, if all else fails and on a server, terminate it then recreate it. That should fix it.
If your problem still persists, please create a support ticket or post in #help in the Discord.