The camera should fire the shutter with the camera set to "shoot without lens". You may simply have an incompatibility with the lens and the camera.
-Demetrius
Current Gear: EOS 5D Mark IV, EF Trinity, EF 50mm F/1.8 STM, EF 85mm F/1.8 USM, 470EX-AI & 600EX II-RT
Retired Gear: EOS 40D & Sigma 17-50mm F/2.8 EX DC OS HSM
-Demetrius
Bodies: EOS 5D Mark IV
Lenses: EF Holy Trinity, EF 85mm F/1.8 USM
Speedlites: 420EX, 470EX-AI, 550EX & 600EX II-RT
