This is a known bug with Genymotion Desktop 3.7.0 on fresh installs - this does not affect users who have upgraded from a previous version.
This problem has now been fixed with Genymotion Desktop 3.7.1.
If you encounter this error, download Genymotion Desktop 3.7.1 installer from https://www.genymotion.com/download/ and upgrade your copy.