I think the 404 is from a stop at step two where the workflow is supposed to continue in with the client secret. Otherwise the call runs smoothly if I use their “navigate to url” instead. I’m trying for their “modal” in this case. 
I attached the doc above, if you have time would mind taking a look? Although I don’t know if that would help you help me diagnose lol.
Is there a way to call a properties.object inside a function? I’ve tried in between brackets but still nothing.