There are two possible causes to this issue:
You are using a virtual device with Android 4.4 or below
Open GApps is not compatible with Android 4.4 and below.
Please use a virtual device with a higher Android version than 4.4.
You have set Genymotion Desktop to use an old or incompatible version of ADB (SDK tools)
- Make sure that your Android SDK tools are up to date.
- If for some reasons you cannot upgrade your SDK tools, set Genymotion ADB to default adb (in-built adb), install the OpenGapps and then revert ADB to your previous custom version.
- Please check our documentation regarding ADB here.