I installed a hot shoe protector on my camera and after a few months realized that was why the built-in flash would not work. My apologies to the world in general, and Canon especially, for my use of inappropriate language prior to figuring out what was going on with my new expensive camera. I called tech support, but all they said was to send the camera for repair if the flash is not working. I am posting this so that others can find the cause and effect relationship. I am the opposite of a professional photographer, so I do not inherently know every little thing about how Canon cameras work.
There is a micro switch in the hot shoe that functions to disable the in-camera flash when an external flash is installed.
The camera isn't smart enough to discriminate between an external flash and a hot shoe protector.
If you look at both sides of the hot shoe rails you can see where the switch is. Then cut back the edge of the protector so that it no longer activates the micro switch.