Playing England in early game, I built a port and ship on Wessex then transtported my army across to Brittany. After taking Brittany, i figured I would go and take Ireland, but for some reason I could not transport my army from Brittany to Ireland. I moved my ship around from the channel to the Irish sea, and Brittany already had a port, but nothing. I even tried building a ship on Brittany, but it would not let me transport across.

Is there something I am doing wrong, or is it a bug?

Thx