Sounds like your unit is a newer ERISIN than mine, connections are slightly different.
You will need to connect 2 wires to the Cars CAN Bus, the ones you need to connect to are under Carpet on Left Rocker Panel, Twisted Pairs one Brown / Red and the other Brown.
There must be 2 wires from H/U that will connect to these twisted's on the car. This is why it is not waking up without Acc Connected
Right, just nicked the pic below, I've added the Red Arrow, that is the CAN Bus wiring, (green Twisteds that my arrow is touching), from H/U which needs to go to Car CAN Connector. I wouldn't mind betting, if you have just plugged the 2 connectors there together, if you look at the Connector on the Car they aren't actually connected, because your old COMAND HU was communicating to the Amplifier via F/O and the COMAND CAN Bus is actually hard wired at the Amplifier
Tell me if that theory is correct or not please, but above you said that your old COMAND only had 3 wires, so no CAN at old COMAND H/U
Regarding the Blue Black on your Car, do not connect this to "SWC & Other Control Cable" Harness in my pic below, see if there is a Blue in the same Harness as the CAN wires, if so connect there, that's how mine is, and Antennas work fine on Radio.
ACC+ should not be Connected nor any of "SWC & Other Control Cable" ................. This is where a lot of the guys having problems are going wrong
This harness is not needed on a CAN Car !!