What is Error 20, “shooting is not possible due to an error”, on a Canon 700D?

I have a Canon 700d and I got an error 20 saying “shooting is not possible due to an error”.

I’ve tried multiple things:

  1. removing battery and reinstalling it

  2. removing sd card and formating it

  3. clean sensor, mirror from the menu

  4. remove and reinstall lens

  5. try different modes

but all the above trials are in vain.

I’ve also tried clicking the shutter button multiple times, but I can’t hear any shutter moving.

Is this a shutter problem, and how can I solve it?