Altium: Harness as output of MultiChannel block
You're using harness connections.

Harness connectors seem to be currently incompatible with the automatic repeat functionality of the MultiChannel design tools.

Unfortunately, the only solution seems to be to break your harnesses out into individual wires.



Hat-tip to Oli Glaser for reminding me I had this problem in the past too.

My completely baseless guess as to why would be that you can't have harnesses in busses, but I don't honestly know.