Solve blank dialog boxes upgrading Server Core to Windows Server 2016

Q. I'm trying to upgrade a Server Core box to Windows Server 2016 but the setup dialog turns blank at one point and I can't continue. What can I do?

A. If you see the following during an upgrade to Windows Server 2016 Server Core you are stuck as you cannot continue the upgrade process.

The solution is to restart the setup (not continuing from the last upgrade attempt) but when calling setup.exe add the "/compat ignorewarning" switch, e.g.

setup.exe /compat ignorewarning

This will solve the problem of the blank screen during upgrade.