With reference to the session recorded 2020.1.18, "Leveraging the Power of
Vision Extensibility" presented by Robert Schmitz and Ryan McErlean,
I tried to reproduce the custom symbol with the Amchart sample without a result.
In fact, the same failure happened in the session itself.
Strange thing is that I asked TechSupport to test out and they said it worked
without any change of code. Their version was the same as mine 2019 version.
As far as I know, the only difference is https and http. We are using http.
I am attaching the code for your reference.