I’m having serious issues with my flashes. I have the 24” mag box, and boobs, 3 speelite ex 600’s and the transmitter. The flashes will not fire when attached or if starting off attached to the mag box. The flash shows a symbol of the flash body with a hexagon and an exlimation point inside. If taken off the mag box, it won’t fire - even when turned off and turned on again. When I take the flash off the box, the hexagon goes away and the normal lines appear, but it won’t fire. When I push the test fire button on the transmitter it fires, but won’t when I push the shutter. Now, if when starting they aren’t attached to the box, they’ll work. Like I had an Indoor wedding where I had two stands on the sides of the isle, and they worked flawlessly. I am so confused. This happened last year and I swear every time I try to troubleshoot at home they fire- but not when it matters- during a session and I end up looking so unprofessional. Someone in another post asked to see the symbol I explained - so they are in the image attached. When I test fired at home they worked as they should. both unattached and attached to the box. I also usually use these in ETTL mode for time sake. Someone please help!!!
We'll need to know more specifics about your camera/flash setup and settings.
What camera do you have? What shutter speed? Perhaps you are attempting to use a shutter above your sync speed and don't have high-speed sync enabled.
For the transmitter, do you have the ST-E3-RT?
Are you using radio control or optical? For radio, when in your venue, did you ensure you were using the best channel? If optical, did you ensure all the flashes can see each other (line of sight)?
I have the R5. Shutter speed was at 250 but I lowered it and adjusted the other settings - I shoot in manual. I typically shoot with the flash in ETTL but tried switching to manual and it still wouldn't fire. The transmitter is the ST-E3-RT. I always use radio - channel 1 and have never had issues. I am ashamed to admit I don't really know how to adjust the settings these things and thus rely on ETTL. I understand Manual, and have used it before, but other than that I have no further understanding. Please be easy on me. lol. If there is a resource to explain what you're talking about I am more than willing to learn. I can try to explain last night's scenario as best I can. I was outside, about an hour before sunset on the water - very bright. The subject was in the shade of a tree with the water to camera right. The box with flash was about 6-7 ft. away - usually I will move it closer to soften it a bit was just trying to see if it would work (since this has happened before). Fresh batteries, flash transmitter, flash, and camera all turned on. Test flash from the transmitter emitted the fire from the flash. It would not fire when I tried with the shutter. I removed the flash from the box and tried with a person simply holding the flash at the subject. Still would not fire. I was right next to the flash in both situations.
The exclamation mark in the right side picture is because the flash is tying to detect the colour of a filter fitted to the flash. On the underside of the 600EX-RT there's a couple of sensors that work with the Canon filter holders, and if you use the Canon filter gels they are identified and the flash can tell the colour of the filter being used to the camera white balance system.
Since your modifier covers the sensors, and it is not readable by the flash you get this icon. You can find this mentioned in page 40 of the manual. Canon expected it could be problematic with non-standard modifiers and also odd-coloured filters, so include a personal function P-Fn 05 to switch filter detection off. On each of your flashes you need to set P-Fn 05 to 1.
To do this, press and hold the ZM/C.Fn button below the left corner of the LCD. After 5 seconds the display changes to custom functions, then press the same button briefly again to reach personal function P-Fn. Turn the dial on the Speedlite to reach P-Fn 05, and then press the SET button and turn the dial to change the value from 0:AUTO to 1:OFF and press SET again.