I encountered this issue in the *invasion england 1945* mission while playing through the *German world campaign 1938-1946* on historic difficulty... I checked every hex along the coastline to make sure that there wasn't just one or two places to embark, like the two town ports which would have been logical but they didn't work either... I tried using every type of ground unit with and without ground transports to see if maybe only infantry could embark but no... I tested to see if it would be only core units or auxiliary units and again, no unit could embark into the ocean from the coastline... Disembarking worked perfectly... I have not tested it in the stand alone scenario only in the campaign... And I've tried restarting the mission from saves and from completing Cherbourg, the mission just prior, again so as to advance to invasion England 1945 naturally as opposed to loading from a saved game