I have the Canon EOS 7d Wireless Transmitter. I also have a Canon Speedlight 550ex and just bought a Canon Speedlight 430ex. So, I set up the two lights on stands, hook up the transmitter. All flashes are on Channel 1, ETTL, and one is on Slave A, the other on Slave B. Slave A (550ex) fires, but Slave B (430ex) does not. WHY? I cannot figure it out. If anyone can offer a little insight, that would be great and I would really appreciate it.