The Hubspace API is figured out. The latest version of the integration (which I no longer develop) has capability to dump the API. If there is a capability not supported, make an issue on github. The new developer is awesome.
You are not seeing traffic because most newer apps need a way to “unpin” the SSL certificate to accept mitmproxy’s certificate. Without that step, mitmproxy can not see the traffic. It wasn’t needed before, but now it is.
I wrote a tutorial a while back (because of another app, not Hubspace), but it is probably out of date. It can get you started. Be prepared to waste hours of time because some methods will not work, but you do not know until you try! MITM Tutorial - #2 by jaaem