Commented Unassigned: NetOffice.ExcelApi.Application.GetActiveInstance return null [20470]

When I've already have excel aplication with opened Workbook
instance = NetOffice.ExcelApi.Application.GetActiveInstance();
returns existing instance and it's correct.
But if the user change cell and leave the cell in Editing-Mode
the result of instance = NetOffice.ExcelApi.Application.GetActiveInstance() is null.

I need use exiting application anyway and not create new. How to get it?

P.S. It doesn't happen using Interop: the result is always correct
instance = (Application)System.Runtime.InteropServices.Marshal.GetActiveObject("Excel.Application");
Comments: ** Comment from web user: rtverd **

I've attached sample