The distech operates as a bacnet router. So treat it like a contemporary controls router. The ECY is essentially transparent between the IP and MSTP sides and cannot itself directly see any of the items on that trunk. The ECY does not act as a supervisor. The intent was to run an AHU on Bacnet IO, and allow the nearby drives to be brought in MSTP to the ECY, and integrated over IP to whatever sup there was.
The IO is available as long as the ECY knows it is there. If the ECY has a compressor status wire landed on IO 1, input 2, you cannot see it. If the ECY has then been told that this input is binary, and it is called compressor status, then you can see it. There is no 'The ECY has the point, knows what it is, but will not tell me'. So it sounds like either the program is missing this or is gone. Which may also explain the lack of routing on the MSTP side.
The good news is that if you have creds for the web ui, you likely have creds for programming, and GFX is easy to get and has no license fees.
Hmmmm....smells like numbatwo to me.