When device rotates after pressing vibration-like icon, this icon disappears preventing the device from rotating back from landscape to portrait. My solution for this is:
rotation setangle 180(user guide documentation)
This will return device again to landscape. I just tried it.
In landscape mode, the Rotate screen button does not appear (for some devices at least) and the CMD + F11 (for mac) did not work for me. I solved this with the following steps:
from landscape, click the Home button (go back to the home screen)
on home screen, press CMD + F11 (for mac)
relaunch the app from the genymotion emulator, this should restore the portrait mode.
Hope this helps someone.