When two applications have a message between them and the two applications belongs to two different city plan zones, then you can draw a channel connecting the two zones. In the channel, the message will show up in the channel connecting the two zones with each other.
In my case I have applicationvariants. I have made a new variant of the applications in each zone. Now the channel will not show the message any more.
Have anyone figured out how to make the channels show message in the channel when using applications variants as endpoints. I have tried to look for an option under shapes and details, but have not found a solution.