I managed to fix it by installing Unreal Engine from Source from github and applyin Isaac_MM suggestion:
[quote]I was able to solve this by adding
CommandletArguments += TEXT(" -UNATTENDED");
to FLocalizationCommandletProcess::Execute in Engine\Source\Editor\LocalizationCommandletExecution\Private\LocalizationCommandletExecution.cpp
It seems the comandlet is trying to open a message box, but as its running via the UnrealEditor-cmd.exe, that’s not possible.
Problem is now with Unreal Source the Metahuman Plugin which is needed for my project is not working anymore but that’s another issue 