External flash on my nikon not working?

External flash on my nikon not working?

Added (1). I have a nikon d90 with a rokinon fisheye lens and I'm using a yongnuo YN568EX speedlite. The speed light works on the hot shoe of the camera with the fisheye but not off camera with my yongnuo YN-622N transceivers. It won't even take a picture even after I turned the flash and the flash cntrl for built in flash on the camera to the manual setting. The speedlite works fine off the camera with the transceivers using my nikon kit lens. I don't know what else to do?

What's the make and model of the flash, what's the model of the Nikon, and what mode(s) are you using? Kind of tough to help diagnose the problem without more information.

For one thing, if you are in certain modes and the camera decides there's enough light, the flash won't go off.

You can force the flash if you are in PASM modes. Just select the Fill flash mode. If you are in Auto or Auto+Slow sync, the camera will decide if you need flash, or not.