Mono.Android reference in Xamarin.Forms is failing

Hi,

I've copied the full solution of an application from one machine to the other.
Both have VS 2017 Community Edition and one of them is showing the following warning:

That results in multiple errors while compiling:

I tried to add the assembly but i get an error:

![](https://us.v-cdn.net/5019960/uploads/editor/du/kpcdzkhwtn1h.png "")

This is working fine in one machine.

Can you help me out?

Thanks