Visual Studio 2015 webtest context parameter not being dereferenced in a URL

Question

I have a (non-coded) Visual Studio webtest where a required context parameter is always successfully extracted from an HTTP Response. Let's call it myParam. In my webtest, I use the context parameter to define a URI in a later HTTP Request, like so: "https://example.net/initial_path/{{myParam}}" where myParam is replaced with its value.

Here is the call where the context parameter (targetId) is successfully extracted. Required=True, so targetId gets a value or the test fails.

Extraction Rule (Must succeed)

On my laptop, this works fine, but after uploading the test to a centralized machine, the context parameter is not getting replaced with its value. In other words, the webtest (contained in a loadtest) is actually requesting the literal string containing {{myParam}}, which of course fails every time.

This is where my context parameter is used in the webtest.

Context Parameter Used in URL

And here is where it is successfully used when the webtest is run from my laptop.

Successful use of Context Parameter

We have a machine running Visual Studio inside the firewall controlling a herd of agents to fully load test our applications. When the same test is run there, the URL uses the literal string {{targetId}} instead of the value stored in the context parameter. Screenshot is from ELK, because this issue isn't a failure within Visual Studio, no logs are generated.

targetId being used as a literal string

My question is: How can I force Visual Studio to recognize my context parameter correctly? It's supposed to do this automatically.