I am including UnityEngine.Analytics on the top of the file

using UnityEngine;
using UnityEngine.Analytics;

but when trying to access

Analytics.CustomEvent() 

I get an error:

Assets/Scripts/Services/GameTracker.cs(44,17): error CS0103: The name `Analytics' does not exist in the current context

To make sure I am not missing something I double checked documentation from:

Unity doesn’t recognize Analytics namespace after update to 5.2. Any ideas / fixes?

Did you tun on Analytics in the Services tab? Go to Window → Unity Services, log in with your id and turn on Analytics. This is new in 5.2. Assemblies will only be loaded when the options are active.