Stumbled into this on Reddit.
Almost a week ago i ran into some problems installing the new radio into the Fiat, got confused and ran out of time and asked for advice. Apparently the included ISO-16PIN harness was fine and i learned some new things. It basically came down to the harness being universal for more models and came pre set up for a Ducato, ACC & ILL where connected through the ISO but the 500 didn't support that (the rest was connected fine). Between the 16pin and ISO was a small connector for those 2 wires, the same connector they use for an optional 5V cooling fan (although those slot in a different port). But on the canbus box was also the same end of the connector and they weren't labelled or mentioned (or i have totally read over it multiple times, i only had a user manual and not an installation manual), so thats where my confusion came from. When switching those connectors so 16pin was going to the canbus box it just worked immediately and i face planted my head against a wall because i wasn't sure about this.