Turns out there were a couple setup errors in the Change of Plans scenario. They were spotted quickly enough that I just decided to overwrite the old file and upload it again rather than give it a new version number. So if you downloaded it before I posted this, make sure to download it again. Check to make sure all of the Allied blocks are in their fleet display.
This is a GREAT Vassal implementation, Rob - thank you - it makes the game a breeze (no pun intended!) to play. Well done.