Hi,
This is a known issue, already in our Database with the ID #195063. It is planned to be fixed in the upcoming hotfixes of ARCHICAD 18 and 19. As a workaround, please switch off the shadow application then switch it on again. For further information and step-by-step help, please visit the HelpCenter: http://helpcenter.graphisoft.com/technotes/operating-systems/windows-10/
Regards,
Katalin Borszeki
Implementation Specialist
GRAPHISOFT