I just purchased the Canon Speedlite 430EX II and for the life of me I can't get the AF Assist light to come on! I shoot in manual on my 5D Mark II, and I have set the flash on ETTL. The guide says the AF assist light is supposed to come on when it senses that it's too dark, but it doesn't. I have checked the custom functions and I have made sure that the AF assist function was enabled.
Am I doing something wrong? Is there some check that I can do to be sure that the flash is properly working?