I realize this is a late reply, but thought I would add it for others' use.
I am using Windows 10 and the "Show Black Screen" setting works inconsistently - sometimes it works and sometimes it doesn't, even though checked. Building on the workaround suggested by kelly_t0, and credit to
http://www.tenforums.com/tutorials/4608-display-switch-shortcut-create-windows-10-a.html, I created two shortcuts:
View Second Screen Only - C:\Windows\System32\DisplaySwitch.exe /external
View Duplicate Screens - C:\Windows\System32\DisplaySwitch.exe /clone
For the Duplicate Screens to work, be sure the TeamViewer "Show Black Screen" is NOT checked, in case it works.
Of course, a solution is always better than a workaround, so I echo kelly_t0 hoping someone can actually resolve the problem.