Testing on Genymotion: Grey Scene except Canvas items

I have a strange issue when testing my app in genymotion.
After unity splash screen I can see for less than a second the entire layout and then all things beyond the main Canvas (on top) becomes gray. Everything is inlcuded into a canvas is shown correctly

It’s a very strange behaviour that I have only in genymotion emulator. Same apk deployed on real device works as expected
I’ve already checked Main camera options (is enabled) and added scene to build
Any suggestion?

Many thanks

Finallly solved! For anyone experiencing this problem, the solution is about modifying shader type.
Any 3d object in the scene must have a material with LEGACY shader
It seems that standard shader are not supported in genymotion, and so everything but canvas item are not showing in the emulator