Does anybody know how to get this combination to work? I received my new Canon Speedlite 430EX III-RT in the mail yesterday and have tried all evening to get it to fire my 270EX II remotely using optical wireless functionality. I've followed the instructions in both manuals (set EX270 II to slave which then should respond to channels 1,2,3,4 and group A, set the 430EX III-RT to 'master' and channel 1,2,3, or 4 and ALL groups). The camera body is a 5D MkIII, with the 430EX III-RT attached. Please help me out, I hope it's not something wrong with my hardware? :-\