I just bought a Yongnuo yn-560 III with two RF-603 transceivers. I also bought a Vello Speedy rotating bracket with a universal Nikon TTL cord. I hooked everything up, put the camera in manual mode and the red light on the flash stayed on and wouldn't fire. I took off the TTL cord, mounted the RF-603 on my D3100 and the flash on the bracket fired. I thought I could fire the flash on the bracket with the universal TTL cord (I know the flash isn't TTL). I also bought a stand and umbrella and the flash with the 603 units works great. Help please!