Thanks for using Elastic APM.
The RUM agent adds a special header called
elastic-apm-traceparent to http request. This header is needed so that the backend agent (in this case .NET agent) knows to use the correct parent ID. However, this header is only added to same-origin requests by default.
Would you please check the http request to see if
elastic-apm-traceparent is added to the headers?
If the request is made to an origin that is different to the one that the page is hosted on, you should add that origin to the
distributedTracingOrigins config on the RUM agent. You can find more information on our distributed tracing guide