Bench testing OBDII dongle
"Unable to Connect..." is a message coming from the ELM inside your OBD2 wifi device. Make sure you look through the documentation thoroughly

You likely need to signal to the ECU that the key is inserted, ignition "on". Otherwise the ECU goes to low power mode shutting down the bus so as to avoid killing your battery.

Look at the wiring diagram from the ACC line-- accessories-- and see where it's coming from-- and going to-- somewhere in there is a wire to the ECU that says "hey, there's a key plugged in here"