On Change and Fire On Change in CRM 2016

The OnChange event doesn’t occur if the field is changed programmatically using the setValue method. If you want event handlers for the OnChange event to run after you set the value, you must use the fireOnChange method in your code.

https://msdn.microsoft.com/en-us/library/gg334481.aspx#BKMK_FieldOnChangeEvent

Xrm.Page.getAttribute(arg).fireOnChange()

https://msdn.microsoft.com/en-us/library/gg334409.aspx