The camera won't take a photo when it cannot detect an electronic connection with an appropriate lens attached. In order to use the Rokinon or any other lens that does not have electrical contacts, you need to go into Custom Menu 1, choose Release Without Lens, and select Disable.
I bought a fisheye (Rokinon) 8mm f3.5 Aspherical Fisheye Lens for Sony Alpha A55 and having problems taking pictures. Set the camera mode dial to M also MF on focus adjustment and shutter speed to -2..1..0..1..2+ to get the proper exposure. Everytime I press the Shutter button,on the screen say, check lens attachment. If the lens is not supported,you can permit use of the lens in the custom menu. I don't understand this explanation. The Lens click during mounting.Can you help me explain in simple ways or some CooL tricks to the above mention. I am missing some instructions to function properly. thanks for your help.