I have a 600EXii-RT problem that I can't figure out. I changed the batteries and now the unit powers on normally, but won't flash, even with the test button. I had been using it for a few hours prior to the battery change and it worked perfectly. No settings on the unit or my camera (5DM4) were changed during the battery swap. I did try replacing the batteries again (they are new and fresh) but to no avail. There are no error messages active on the flash or camera, and the ready light stays red. The flash unit is a few years old, but has less that 500 flashes on it, very seldom used. Any ideas would be greatly appreciated.
No, the flash will not trigger on or off the camera. Everything else works perfect. Even the green proper exposure light works.
Assuming that there are no issues associated with the batteries, then it sounds like your Speedlite needs service. It could be as simple as a flash tube.
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