EOS 5D Mark IV - Error 20

[WNCphoto]

I have a Error 20 message on my EOS Mark IV. I have turned it off an on, tried different lenses and swapped batteries. It has been suggested that I send the camera to Canon for shutter repair. How does this process work?

[deebatman316]

What lenses are you using Canon or 3rd Party are any battery grips being used external flashes/ speedlites. Does the camera work with the memory cards removed.

[WNCphoto]

Thank you for your response. I use the 24mm-105mm kit lens and the EF 300mm 1:4 L IS lens. No 3rd party equipment, no battery grips or external flashes/speedlites. The camera does not work with or without the memory card.