I have been having issues with data not coming through in the elastic APM. I have implemented the solution as documented by Elastic Team.
I have set up the following.
added this in my web.config file. 
This does not work, I have this error in my output.
After looking into the output error, I looked at all possible solutions and updating one of my packages fixed the error. I had to upgrade “Data Flow Task” to the latest version 7. This package is responsible for data transformation between source and the destination.
Make sure the default project is targeting the API... NuGet\Install-Package System.Threading.Tasks.Dataflow -Version 7.0.0