My keyboard for my imac is not working.

You can try doing a SMC reset with a wired keyboard, if that doesn't work the keyboard may need to be replaced.

SMC RESET

• Shut down the computer.
• Unplug the computer's power cord and all peripherals.
• Press and hold the power button for 5 seconds.
• Release the power button.
• Attach the computers power cable.
• Press the power button to turn on the computer.

PRAM RESET

• Shut down the computer.
• Locate the following keys on the keyboard: Command, Option, P, and R. You will need to hold these keys down simultaneously in step 4.
• Turn on the computer.
• Press and hold the Command-Option-P-R keys. You must press this key combination before the gray screen appears.
• Hold the keys down until the computer restarts and you hear the startup sound for the second time.
• Release the keys.

I've never heard of Assist settings, exactly what are you referring to?

I see, I believe you are referring to System Preferences - Universal Access - Keyboard tab.

Your welcome, glad you got it figured out!