Well, I am not sure which one of the two seat map methods you were actually referring to, but I just tried them both for the flight in question, and they both worked OK ...
Are you using an up-to-date version of the Tool?
Of course ... level is 2.8.1 ... and since I am only
GOLD I have no access to the
Textual version so it would have to be the
Graphical Version. Oh well - still giving me the same message ... no time to play with it this evening...