HarryM Loc: NYC (now in Florida)

Have a Canon T6i, suddenly external flashes will not work. Internal flash is OK. Batteries are good. Anyone have any ideas ?

jdubu Loc: San Jose, CA

Multiple external flashes? check your hot shoe... check your flash settings in the menu... if it's only one speedlight, what is it? Does it flash when you press the test button? Do you have more information to share?

CO

If your camera and speedlite have off-camera triggering capability, give that a try. If that works it would indicate that something is wrong with the communications between the camera and flash through the hot shoe contact pins.

sirlensalot Loc: Arizona

First things first. Try cleaning contacts on hot shoe and flash. Denatured alcohol works pretty good.

Peterff Loc: O'er The Hills and Far Away, in Themyscira.

Which external flashes do you have? Do they work on the hot shoe? Do they work remotely? Have you reset the flash to original settings? There are many things that could cause mis communication either with the camera settings or the flash settings. Check the channel settings for flash control if remote.

amfoto1 Loc: San Jose, Calif. USA

I don't have that specific model, but many Canon cameras have a "prevent flash from firing" setting in the menu. Check to see if your camera has that and how it's set.

This feature is used when you want the autofocus assist feature of a flash, but don't want the flash to fire. I spent hours trying to figure out what was wrong with one of my Canon, why it wouldn't fire a flash... before someone on a forum suggested I check that setting. Sure enough... somehow I'd disabled flash! Reset it and all was fine.

Otherwise...

It sounds as if you have tried multiple external flashes... Is that correct? If it is the case, then it's probably the camera and not the flash that's failed for some reason. If it were a single flash, I'd recommend trying it on another camera just in case the flash itself has failed. But it would be odd for multiple flashes to fail at the same time.

It also sounds as if the external flashes worked okay with the camera in the past, but now no longer do. Is that right? If so, it also suggests that something is set incorrectly. What have you changed recently? If you can't find anything, you might try "reset" in the menu. But if you do, just be aware that you'll lose other settings you've made.

Also, are you using the external flash in the hot shoe or using off-camera with wireless communication? The off-camera flash might need to be set to "slave" mode. The built-in flash is used to "communicate" with and control the off-camera flash... but that has very limited range.

BebuLamar

I don't know about the T6i as I don't have one nor I know much about Canon camera. I wonder if there is a setting that you can set to prevent the camera from firing the external flash? If not then possibly the flash firing circuit is fried like using a flash with high sync voltage.

speters Loc: Grangeville/Idaho

Need a lot more info, trying to pinpoint your problem! What have you done so far? What did you check so far? etc. Do you have the same channels that on all devices? Well you didn't even say, what means of communication you're using between your flashes and your camera!!