Had this happen to me not to long ago I put everything and pictures on the forum. Does your remote button work when you push the trunk button?
I traced it to the wires that go from body to trunk lid the loom that is on the passenger side protected with rubber. I found wires broken inside, I traced it for days.
If you have no voltage at the connector to the latch or weird voltage then the wire is broken.
Sent Via iPhone using BimmerApp